Ukraine's president has said there is "nothing left" of the city of Mariupol after weeks of Russian bombardment, and Kyiv appealed to Moscow to allow the evacuation of at least 100,000 people who want to leave.
Ukraine has issued increasingly dire warnings about the situation in the encircled southern port city, where officials say residents are without food, medicine, power or running water.
Officials have said 300,000 civilians were also running out of food in the occupied southern Ukrainian city of Kherson, highlighting what an international aid official said was the breakdown of Ukraine's humanitarian system.
"There is nothing left there. Only ruins," President Volodymr Zelensky said of Mariupol, which has a peacetime population of 400,000, in a video address to the Italian parliament.
As he was speaking, the city council said Russian forces had dropped two large bombs on Mariupol but gave no details of casualties or damage. Reuters could not independently verify the report. Russia did not immediately comment on it.
"Once again it is clear that the occupiers are not interested in the city of Mariupol. They want to level it to the ground and make it the ashes of a dead land," the council said.
Russia denies targeting civilians and blames Ukraine for the repeated failure to establish safe passage for civilians out of Mariupol. Ukraine defied an ultimatum for the city to surrender by dawn on Monday as a condition for Russian forces to let civilians leave safely.
"We demand the opening of a humanitarian corridor for civilians," Deputy Prime Minister Iryna Vereshchuk said on Ukrainian television.
She later added: "There are at least 100,000 people who want to leave Mariupol but cannot."
Ms Vereshchuk said that unless a safe corridor was created and buses were allowed in to evacuate them, they would have to walk from 10 to 20 km to reach relative safety - a risky journey if there is no ceasefire.
She and other Ukrainian officials said Russian forces were also preventing humanitarian supplies reaching civilians in Kherson, a city they control.
"Kherson's 300k citizens face a humanitarian catastrophe owing to the Russian army's blockade. Food and medical supplies have almost run out, yet Russia refuses to open humanitarian corridors to evacuate civilians," foreign ministry spokesperson Oleg Nikolenko said on Twitter.
Russia did not immediately comment on the situation in Kherson. It calls its military actions a "special military operation" to disarm Ukraine and protect it from "Nazis". The West calls this a false pretext for an unprovoked war.
Mr Zelensky said all issues would be on the table if Russia's Vladimir Putin agreed to direct talks to end the war, including contested Crimea and Donbas, but he warned his country would be "destroyed" before it surrenders.
On the ground, there was no let-up in the violence, with Kyiv under a new 35-hour curfew after Russian strikes reduced a Kyiv shopping centre to rubble, and the Pentagon saying Moscow was stepping up air and sea operations.
Nearly a month into the conflict, there has been little progress in talks between the two sides, and Mr Zelensky has repeatedly urged direct discussions with his Russian counterpart.
He insisted again yesterday that a meeting with Mr Putin "in any format" was needed to end the war.
"If I have this opportunity and Russia has the desire, we would go through all the questions," he told Ukrainian journalists in an interview published by media outlet Suspilne.
"Would we solve them all? No. But there is chance, that we partially could - at least to stop the war," he added.
Mr Zelensky said he was even willing to discuss Russian-occupied Crimea and the breakaway Russian regions in Donbas, though he insisted he still believes they must be returned to Ukraine.
"At the first meeting with the president of Russia, I am ready to raise these issues," he said, adding that any agreement involving "historic" changes would be put to a national referendum.
"This is a very difficult story for everyone. Crimea and Donbas ... And to find a way out, we need to take this first step, which I spoke about: security guarantees, the end of the war," he added.
He repeated his assertion that Ukraine "already understood" it could not join NATO, but he added that his countrymen would not simply "hand over" the capital, the eastern city of Kharkiv, or Mariupol.
"Ukraine cannot fulfil Russian ultimatums," he said. "We should be destroyed first."
Russia has stepped up its military activity, flying 300 sorties in the past 24 hours, in a "desperate" bid to turn the tide against the Ukrainian resistance, a senior US defence official said.
"They are also suggesting that Ukraine has biological and chemical weapons in Ukraine. That's a clear sign he's considering using both of those," Mr Biden said, without offering additional evidence.
Even in areas Russia has captured, resistance has continued, with Ukraine's leaders accusing Russian troops of firing on unarmed protesters in the occupied southern city of Kherson
A series of videos posted on social media and the messaging app Telegram showed citizens gathering in Kherson's "Freedom Square" protesting against Russia's recent seizure of the city.
Russian soldiers could be seen firing into the air, and video footage showing a bleeding elderly man being carried away, though local officials said there were no fatalities.
Away from the frontlines, diplomatic manoeuvring will continue this week with Mr Biden flying to Europe for talks with G7, EU and NATO leaders.
Ukraine said Russian troops used stun grenades and gunfire to disperse a rally of protesters in the occupied city of Kherson today. CCTV footage obtained by Reuters showed several hundred protesters in Kherson's Freedom Square running to escape. | Read: https://t.co/DrqAew0tbt pic.twitter.com/kg3KbaHr9o
— RTÉ News (@rtenews) March 21, 2022
Western countries and allies are expected to shore up their united front, though possible additional steps to pressure Russia remain unclear.
Moscow has warned relations with Washington are "on the verge of rupture," after Mr Biden branded Mr Putin a "war criminal".
It said it was abandoning talks with Japan, aimed at reaching a post-World War II peace treaty, citing Tokyo's "openly hostile position".
Mr Zelensky has urged Europe to significantly dial up pressure on Moscow, saying the continent must cease all trade with Russia, but Germany has pushed back on a call for an EU embargo on Russian oil and gas.
At the Kremlin, spokesman Dmitry Peskov warned such an embargo would "have a very serious impact on the world energy market", where oil prices are already sky-high.
With the war edging closer to a stalemate, Mr Zelensky has also appealed to China, urging it to "play an important role in" ending the conflict.
The war has displaced around 10 million Ukrainians, with around a third becoming refugees, according to the UN, and sparked fears of famine elsewhere because Russia and Ukraine are both major agricultural exporters.
Signs of Ukrainian forces 'going on the offensive' - Pentagon
Ukraine forces have reversed the battlefield momentum against invading Russians in some areas to reclaim ground in recent days, the Pentagon has said.
The Ukrainians are "in places and at times going on an offensive," particularly in the south of the country, US Defense Department spokesman John Kirby told CNN.
"They are going after Russians and pushing them out of places where the Russians have been in the past," he said, particularly in Mykolaiv.
"We have seen this now increase over the last few days."
Mr Kirby said he could not confirm reports from Ukrainian officials that they had retaken at least one town and expect to take more in coming days.
But it would be "consistent with the kind of fighting and the kinds of capabilities we have seen the Ukrainians use," he said.
As for the Russians, he echoed Western analysts who have said the invading forces have become bogged down.
"They are running out of fuel. They're running out of food. They are not integrating their operations in a joint manner the way you would think a modern military would," Mr Kirby said.
He said Russian commanders "aren't necessarily talking to one another," and that there were communication problems between air and ground forces.
In some cases the Russian fighters have had to resort to using cellphones to communicate with each other.
The Russians are "frustrated" and "stalled," he said, citing the fact Moscow's forces have failed to take control of population centers beyond two areas around Kherson and Melitopol in the south.
"They are slowed. And some of that... is due to their own ineptitude."
The Chairman of the Ukraine Centre for Defence Reform said he believes Russia "will have no chance to win the war."
Oleksandr Danylyuk said Ukraine's goal is to "change the regime in Russia" and stop the invasion, which he said his country will do.
Speaking on Prime Time from the capital Kyiv, he said winning the war was one way out of the conflict and he claimed that Ukraine has "ten time less causalities than Russia."
Mr Danylyuk said what Russia is doing "is completely illegal" according to the international law and he has accused Moscow of a "violation of all of the international security system built after the end of the Second World War."
He said Vladimir Putin is trying "to force Ukraine to capitulate and to sign some agreements to recognise that Russia has a right to change Ukrainian territorial integrity and to undermine Ukrainian sovereignty."
