Moscow has warned that it will view any bid by the West to guard Ukraine's airspace as an act of hostility, as the United States said it was seeking ways to help Poland provide warplanes to its neighbour and Kyiv pleaded for Nato help against Russian bombardment.
Russia’s ground forces face fierce resistance from Ukraine’s troops 11 days after invading, but Moscow’s air power is inflicting a heavy toll on Ukrainian civilians and infrastructure such as schools and hospitals, as well as on military sites.
Ukrainian officials said plans to evacuate 200,000 civilians from the port of Mariupol failed for a second day because of Russian shelling on Sunday, when missiles also destroyed Vinnytsia airport and hit Irpin, 25km from Kyiv, as residents tried to flee. At least three civilians were killed.
"Eight missiles against our city, against our peaceful Vinnytsia, which has never posed a threat to Russia in any way. A brutal, cynical missile strike has completely destroyed the airport," said Ukrainian president Volodymyr Zelenskiy.
"We repeat every day: 'Close the sky over Ukraine! ' Close it for all Russian missiles, Russian combat aircraft, for all these terrorists . . . You can do it," he added in a video address to western leaders.
“If you do not do that – if you at least do not give us aircraft for us to be able to protect ourselves – there can be only one conclusion: You also want us to be slowly killed.”
US secretary of state Antony Blinken said Washington was looking "very, very actively" at ways for Poland to provide warplanes to Ukraine and for the US to then plug holes in Polish air defences.
“That gets a green light,” he told US television. It is not clear whether Warsaw supports such a plan, however.
Russian defence ministry spokesman Igor Konashenkov said "we know for sure that Ukrainian combat aircraft have flown to Romania and other neighbouring countries".
“The use of the airfield network of these countries for basing Ukrainian military aviation with the subsequent use of force against Russia’s army can be regarded as the involvement of these states in an armed conflict,” he warned.
Russian president Vladimir Putin said any attempt to impose a no-fly zone over Ukraine would "be considered by us as participation of the respective country in an armed conflict".
As major corporations continued to leave Russia and it sank deeper into economic isolation, Mr Putin said a new avalanche of sanctions against his country “are akin to a declaration of war; but thank God it has not come to that”.
Mr Putin spoke to the leaders of France, Turkey and Israel but made clear he intended to continue an invasion of Ukraine that has killed thousands of people and displaced about 1.5 million.
His attack on Ukraine – with the supposed aim of “denazifying” and “demilitarising” the pro-western democracy of 41 million people – has been accompanied by a further crackdown on dissent in Russia, where thousands have been arrested at anti-war protests.
Pope Francis has sent two cardinals to Ukraine, where he said "rivers of blood and tears are flowing".
