People sit around a lamp in a bomb shelter in Mariupol, Ukraine, Sunday, March 6, 2022. Photo / AP

The Ukrainian government has accused Russia of breaking a ceasefire agreement, by shelling a route intended to allow civilians to escape the besieged city of Mariupol.

Residents of the port city are under intense bombardment by Russian troops, and also living without heat, water, sanitary systems or phones.

Around two million people have fled Ukraine since the war began less than two weeks ago, the UN refugee agency has reported.

Meanwhile, military experts said Russia is overcoming its logistics problems and could mount an assault on Kyiv within a matter of days.

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According to the World Health Organisation, attacks on Ukrainian hospitals, ambulances and other healthcare facilities have increased "rapidly" over the last few days and vital medical supplies are running low.

The UN agency said it was working to urgently get medical supplies to Ukraine.

Ukraine is running low on medical items such as oxygen, PPE, blood products, insulin and surgical supplies.

Russia's Central Bank has announced a new policy, allowing Russian citizens with foreign currency accounts to withdraw up to US$10,000 until the 9th of September.

Anything above that amount will have to be withdrawn in rubles at the market rate.

⚡️Russia suspends sale of foreign currency. Customers will be able to withdraw a maximum of $10,000 in foreign currency from their accounts. All other funds will now be paid in rubles.

⚡️ Fitch downgrades Russian credit rating to imminent default. “The ‘C’ rating reflects Fitch’s view that a sovereign default is imminent,” the credit agency said in a statement.

Corpses lie in the streets of Mariupol. Hungry people break into stores in search of food and melt snow for water. Thousands huddle in basements, trembling at the sound of Russian shells pounding this strategic port city.

"Why shouldn't I cry?" Goma Janna demanded as she wept by the light of an oil lamp below ground, surrounded by women and children. "I want my home, I want my job. I'm so sad about people and about the city, the children."

A humanitarian crisis is unfolding in this encircled city of 430,000, and Tuesday brought no relief: An attempt to evacuate civilians and deliver badly needed food, water and medicine through a designated safe corridor failed, with Ukrainian officials saying Russian forces had fired on the convoy before it reached the city.

Nearly two weeks into the invasion, the Russians have advanced deep along Ukraine's coastline in what could establish a land bridge to Crimea, which Moscow seized from Ukraine in 2014. Mariupol, which sits on the Azov Sea, has been surrounded by Russian soldiers for days.

Mariupol, said Ukrainian Deputy Prime Minister Iryna Vereshchuk, is in a "catastrophic situation."

Images showing people lining up outside McDonald's in Russia on the day the company announced it would stop operating in the country have been shared online.

In #Russia, people lined up at McDonalds pic.twitter.com/TQtsxndibi

Estee Lauder, Shell, Starbucks, Coca-Cola and PepsiCo have also announced they have suspended operations in Russia.

The boycott by several big global corporations is having a major impact on the country's economy, with the ruble hitting a new record low on Monday.

Ruble has hit 140. Absolute madness

Following similar announcements earlier today from McDonald's and Starbucks, Coca-Cola and PepsiCo have also announced they are suspending operations in Russia.

In a statement, Coca-Cola said it is "suspending its business in Russia".

"Our hearts are with the people who are enduring unconscionable effects from these tragic events in Ukraine," the statement continued.

"We will continue to monitor and assess the situation as circumstances evolve."

PepsiCo made a similar announcement today as well, saying it will be suspending all capital investments, advertising, and promotional activities in Russia. The company also said it will stop operations in Ukraine to allow associates to seek safety as war escalates in the country.

One of the two Russian warships that attacked Snake Island, a sliver of land in the Black Sea, has been destroyed, according to Ukrainian military sources.

The Vasily Bykov, a large patrol corvette commissioned in December 2018, appears to have been hit during a firefight in the early hours yesterday.

Video shared by the Ukrainian navy showed rocket exchange, followed by the sound of two men trying to work out whether they hit the ship.

"We f***ing hit them", one of the men confirms.

The second man invokes the Ukrainian soldier's words from when the island was attacked, saying: "Russian warship, go f*** yourself."

A TikTok video shows six Ukrainian women in military gear pledging to "destroy the enemy".

The Ukrainian women, wielding machine guns, sent a chilling Women's Day message where they vowed to avenge the death of every child killed in the Russian invasion of Ukraine.

Wearing combat gear and holding machine guns and assault rifles, with the Ukrainian flag as backdrop, the women pledge to "destroy the enemy on every inch of Ukrainian land".

"We are women of Ukraine," one of the women says at the start of the video.

"We have blessed our men to protect our land. We have already taken our children to safety, we join the men and the Ukrainian army," she adds. "In every city, village, forest and field. For every child, woman, old man, damaged houses and streets - we will shoot you like rabid dogs," the women pledge.

"Glory to Ukraine - death to enemies."

Around two million refugees, mainly women and children, have fled the country in what is the largest humanitarian crisis since WWII.

Poland said Tuesday it would give all of its MiG-29 fighter jets to the US, potentially advancing an arrangement that would allow the warplanes to be passed along to Ukraine's military as it confronts invading Russian forces.

⚡️ Poland to supply the U.S. with its entire stockpile of MIG-29 jets, free of charge. The planes are then expected to be shipped to Ukraine. The Polish government asked other NATO members to follow the country’s example.

International security expert David Welch, who is based in Canada, said on the AM Show that the threat of a nuclear attack was real if Putin was feeling irrational, stressed and if he felt like he was losing the battle.

Putin wanted his troops to operate in Ukraine and didn't want a radiated battlefield so would be aiming elsewhere.

He told AM he would be stunned if there were a scenario that Russian military planners had even considered where Putin initiated the use of weapons when Russia was not under attack. Russian doctrine was to only use nuclear weapons for self defence.

He imagined it would be some kind of demonstration shot or series of demonstration shots.

"I wouldn't want to be the Russian planner whose job it was to try and pick those. I don't think I would want to pick capital cities in decapitation efforts because I would want to have senior leaders in other countries to talk to and negotiate something down the road."

He said they would probably aim for a naval base or airfield in Europe or the US and it would be a "reckless act" to only signal seriousness on Putin's part. "And what does he follow up with?"

Some countries had been attacked in the past and had decided not to respond, he said.

There had been a lot of prudent restraint from Biden and other leaders of other countries in Putin's earlier nuclear alert, but Welch said the pressure to retaliate if there was an attack on a Western base would be "very very intense" and it would be interesting to know what the conversation would be and if they would retaliate.

President Joe Biden announced this morning (NZ time) that the US will ban all Russian oil imports, toughening the toll on Russia's economy in retaliation for its invasion of Ukraine. But he acknowledged it will bring costs to Americans, particularly at the gas pump.

The action follows pleas by Ukrainian President Volodymyr Zelenskyy to US and Western officials to cut off the imports, which had been a glaring omission in the massive sanctions put in place on Russia over the invasion. Energy exports have kept a steady stream of cash flowing to Russia despite otherwise severe restrictions on its financial sector.

"We will not be part of subsidising Putin's war," Biden declared, calling the new action a "powerful blow" against Russia's ability to fund the ongoing offensive.

He warned that Americans will see rising prices, saying, "Defending freedom is going to cost."

Biden said the US was acting in close consultation with European allies, who are more dependent on Russian energy supplies and who he acknowledged may not be able to join in immediately. The announcement marked the latest Biden attempt at cutting off Russia from much of the global economy and ensuring that the Ukraine invasion is a strategic loss to President Vladimir Putin, even if he manages to seize territory.

"Ukraine will never be a victory for Putin," Biden said.

The European Union this week will commit to phasing out its reliance on Russia for energy needs as soon as possible, but filling the void without crippling EU economies will likely take some time. The UK announced that oil and oil products from Russia will be phased out by the end of the year.

Russia cannot sustain its air losses for more than a fortnight after at least nine aircraft were shot down in just 24 hours, analysts have said.

Defence analysts said Moscow had been unable to establish air superiority because of its inability – so far at least – to mount "complex" strikes capable of knocking out Ukraine's air force and ground-to-air missile systems.

Western officials have been surprised by Russia's inability to win the battle in the skies given its huge air advantage. Without air superiority, large, slow-moving convoys on the ground can be picked off by Ukrainian drone strikes and shoulder-held anti-tank missiles, supplied to Ukraine by the West.

Military strategists suggest that if Kyiv, the capital, and Kharkiv, in the east, continue to resist the invasion then Vladimir Putin's war effort will falter after "no more than three weeks" unless a major resupply effort is undertaken.

The US and Britain - and oil company Shell - announced overnight (NZ time) they are banning imports of Russian oil, the latest sanctions intended to punish Moscow for its invasion of Ukraine.

And Ukrainian President Vloldomyr Zelenskyy received loud applause before and after a historic speech to the House of Commons in London via videolink.

Zelenskyy told British politicians that Ukrainians don't want to lose their country to Russia, just as Britain didn't want to lose its country to the Nazis.

He referenced Winston Churchill's World War II speech, saying Ukraine will fight to the end, at sea and in the air.

Zelenskyy says Ukraine will continue fighting for its land whatever the cost, in the forests, in the fields, on the shores, and in the streets.

He asked UK Prime Minister Boris Johnson to increase the pressure of sanctions against Russia, recognise it as a terrorist state, and ensure Ukrainian skies are safe.

Of the more than 50 children now killed in the invasion, Zelensky said: "These are the children that could have lived, but these people have taken them away from us".

In New Zealand, Immigration Minister Kris Fa'afo'i says the Government's announcement to help fast-track support for Ukrainians both in the country on a visa already, and those seeking to enter, is a good start.

He told TVNZ's Breakfast show that it was a commitment and a move that is the start of making an awful situation no worse.

"It is a start and, as I say, we will do more."

Fa'afo'i says they will be considering all the factors involved in this current situation, including people's eligibility to access a visa into New Zealand and looking at who would be eligible to come into the country - including Ukrainian Kiwis' parents or other relatives.

"We want to make sure we work carefully through those issues."

The minister acknowledged the humanitarian aid New Zealand had offered to help those surrounding countries now taking in the up to two million people who have fled Ukraine.

Fa'afo'i said the Government would also look at what may be needed to help Ukrainians here take in relatives from their motherland.

"The Russians have not planned for a long war nor made provisions to sustain it over time," said Lawrence Freedman, emeritus professor of war studies at King's College London.

Russian military losses are being catalogued by observers relying only on visible and verified images, such as a crashed jet or burned-out tank, posted on social media or recorded by journalists.

The true losses may be higher as a consequence, but verified photographs and footage show that 11 Russian planes, 11 helicopters and two drones have been shot down since the invasion began 12 days ago, including nine over the weekend.

Russian jets destroyed include at least four Su-34 fighter/bomber aircraft, four Su-25 ground attack fighters, two Su-30 fighter jets and nine attack helicopters. The economic cost is huge, estimated at almost a quarter of a billion pounds for warplanes alone.

US defence intelligence official said in a briefing that emerged overnight: "We continue to observe that the airspace over Ukraine is contested. Ukrainian air and missile defences remain effective and in use. The Ukrainian military continues to fly aircraft and to employ air defence assets.

"Both sides have taken losses to aircraft and missile defence inventories. We are not going to speak to numbers. We assess that both sides still possess a majority of their air defence systems and capabilities."

The numbers have been catalogued by Stijn Mitzer, a conflict analyst, who has been posting under the Twitter name Oryx and on a website of the same name. The website said: "This list only includes destroyed vehicles and equipment of which photo or videographic evidence is available. Therefore, the amount of equipment destroyed is significantly higher than recorded here."

Defence analysts said Ukraine still had a number of fighter jets operating from airfields in the west of the country and surface-to-air missile sites, some mobile, that Russian forces have been unable to identify and destroy.

The success of surface-to-air missile strikes has forced Russian jets to fly lower, giving them cover from missile attacks but leaving them vulnerable to attack from hand-held portable air-defence systems–guided rockets.

Justin Bronk, research fellow for airpower at the Royal United Services Institute, the UK's leading defence and security think tank, said: "The loss rate becomes unsustainable very fast. If you keep that loss rate up for a couple of weeks, that becomes a real problem for the Russians. They lost nine aircraft over the weekend. That is a lot."

He said Russian cruise missiles had been deployed to hit airfields at the start of the invasion but such weapons, while useful for targeting "fixed infrastructure, hard standings and cratering runways", were less effective at knocking out smaller targets such as fighter aircraft.

He suggested runways could be quickly repaired and fighter jets removed from conflict zones in eastern Ukraine and redistributed in the west of the country ready for deployment. Ukraine had fewer than 100 combat aircraft at the start of the war, and it is unclear what remains after days of conflict.

"Ukraine is still flying," said Bronk, who added that the "continued absence" of major air operations mounted by Russia raises "serious questions" about its capability.

He said: "While the early VKS [Russian air force] failure to establish air superiority could be explained by lack of early warning, coordination capacity and sufficient planning time, the continued pattern of activity suggests a more significant conclusion – that the VKS lacks the institutional capacity to plan, brief and fly complex air operations at scale."

He said if Russia could conduct "complex air operations", Moscow should by now have achieved air superiority by hunting down Ukrainian surface-to-air missile sites.

After its failure to decapitate Ukraine's leadership in the opening days of the war, Russia is left with the prospect of a humiliating defeat or pressing on with ever greater violence, experts warn.

Moscow on Monday seemed to water down its earlier demands of Ukraine. A Kremlin spokesman said hostilities could stop "in a moment" if Ukraine ceased fighting, amended its constitution to remove any possible future in Nato, acknowledged the loss of Crimea and recognised the separatist areas in the east of the country.

Any mention of "de-Nazifying" Ukraine – seemingly important enough for Russia to have invaded – was dropped.

But defence experts have said any prospect of military defeat or stalemate – which would be seen as a tactical victory for Ukraine – could mean increased violence in the coming days, particularly against civilians.

The US and Britain are banning imports of Russian oil, the latest sanctions intended to punish Moscow for its invasion of Ukraine.

US President Joe Biden announced the country is "targeting the main artery of Russia's economy" by banning the imports.

British Business Secretary Kwasi Kwarteng said oil and oil products from Russia would be phased out by the end of the year.

He said the transition period "will give the market, businesses and supply chains more than enough time to replace Russian imports", which account for eight per cent of UK demand.

Kwarteng said the UK would work with its other oil suppliers, including the US, the Netherlands and the Gulf states, to secure extra supplies.

The bans followed pleas from Ukrainian President Volodymyr Zelenskyy to US and Western officials to cut off the imports, which had been a glaring omission in the massive sanctions put in place on Russia over the invasion.

Buses carried civilians out of an embattled Ukrainian city on Tuesday along a safe corridor agreed to by the two warring sides, while a parallel effort to relieve the besieged port of Mariupol was thrown into jeopardy by reports of renewed Russian shelling.

Europe's worst refugee crisis since World War II grew even more severe, with UN officials reporting that two million people have now fled Ukraine.

Moscow's forces have laid siege to Ukrainian cities and cut off food, water, heat and medicine in a growing humanitarian disaster. But for days, attempts to create corridors to safely evacuate civilians have stumbled amid continuing fighting and objections to the proposed routes.

On Tuesday (Ukraine time), a convoy of buses packed with people fleeing the fighting moved along a snowy road from Sumy, a northeastern city of a quarter-million people, according to video from the Ukrainian communications agency.

Ukrainian Deputy Prime Minister Iryna Vereshchuk said they were headed southwest to the Ukrainian city of Poltava, and included students from India and China.

Hours before the convoy reached Sumy, overnight strikes killed 21 people there, including two children, Ukrainian authorities said.

Meanwhile, buses emblazoned with red cross symbols carried water, medicine and food towards the encircled southern port of Mariupol, scene of some of the worst desperation. Vereshchuk said the vehicles would then ferry civilians out of the city of 430,000 people.

But soon after officials announced that buses were on their way, Ukrainian authorities said they had learned of shelling on the escape route.

It was unclear whether the supply convoy made it to Mariupol. It appeared unlikely that civilians would be able to board the buses to get out.

The deputy mayor of Mariupol cast doubt on the evacuations, telling the BBC that Russian forces continued to pound areas where people were trying to gather ahead of being taken out. He said some roads were blocked, while others were mined.

"So we cannot establish sustainable cease-fire and safety route at the moment,″ Serhiy Orlov said. "So we still have a city in blockade."

The city is without water, heat, working sewage systems or phone service. Residents have been getting water from streams or by melting snow. Corpses lay in the streets, and authorities planned to start digging mass graves for the dead.

With the electricity out, many people are relying on their car radios for information, picking up news from stations broadcast from areas controlled by Russian forces or Russian-backed separatists.

Looting has become widespread for food, clothes and even furniture, with locals referring to the practice as "getting a discount".

In a video address from an undisclosed location, Zelenskyy said a child had died of dehydration in Mariupol, another sign of the city's desperation.

Nearly two weeks into the fighting, Russian forces have captured a swath of southern and coastal Ukraine but have seen their advances stopped in many areas — including around Kyiv, the capital — by nimble Ukrainian fighters targeting Moscow's armoured columns.

Thousands of people are thought to have been killed, both civilians and soldiers, though the actual number remains unknown.

The fighting has caused global economic turmoil, with energy prices surging worldwide and stocks plummeting. It also threatens the food supply of millions around the globe who rely on crops farmed in the fertile Black Sea region.

Western countries have rushed weapons to Ukraine and moved to slap Putin's Russia with sanctions.

Ukraine's military said Ukrainian forces continued defence operations in the Mariupol suburbs.

The military said "demoralised" Russian forces are looting, commandeering civilian buildings and setting up firing positions in populated areas. The claims could not be independently verified.

The battle for Mariupol is crucial because its capture could allow Moscow to establish a land corridor to Crimea, which Russia seized from Ukraine in 2014.

Oleksiy Kuleba, governor of the Kyiv region, said Ukraine was also making arrangements to get people out of the suburb of Irpin.

Late Tuesday, Zelenskyy released a video showing him standing near the presidential offices in Kyiv. Behind him were piles of sandbags, a snow-dusted fir tree and a few cars.

It was the second video in 24 hours showing him near the country's seat of power, apparently made to dispel any doubts about whether he had fled the city.

"Snow fell. It's that kind of springtime," he said in a soft voice. "You see, it's that kind of wartime, that kind of springtime. Harsh. But we will win."

McDonald's said it is temporarily closing all of its 850 restaurants in Russia in response to the country's invasion of Ukraine.

The burger giant said it will continue paying its 62,000 employees in Russia "who have poured their heart and soul into our McDonald's brand".

But in an open letter to employees, McDonald's president and CEO Chris Kempckinski said closing those stores is the right thing to do for now.

"Our values mean we cannot ignore the needless human suffering unfolding in Ukraine," Kempczinski said.

Kempczinski said it's impossible to know when the company will be able to reopen its stores.

McDonald's has also temporarily closed 100 restaurants in Ukraine and continues to pay those employees.

McDonald's could take a big financial hit because of the closures. In a recent regulatory filing, the Chicago-based company said its restaurants in Russia and Ukraine contributed nine per cent of its annual revenue, or around $2 billion.

Unlike other big fast-food brands in Russia that are owned by franchisees - including KFC, Pizza Hut, and Burger King - McDonald's owns 84 per cent of its Russian locations.

Pressure has been mounting for McDonald's and other companies like Coca-Cola and PepsiCo that remain in Russia to pull out. Many corporations have ceased operations in the country in protest of the Ukraine invasion.

- Additional reporting by AP and news.com.au