Ukraine has pleaded with the West to help protect its skies after blaming Russia for a bomb strike that gutted a maternity hospital in the besieged port of Mariupol.
Two weeks after Russia invaded its pro-western neighbour, fighting raged outside major cities including the capital Kyiv, fears grew for the safety of the decommissioned Chernobyl nuclear power plant after its electricity supply failed, and Ukrainians continued to join a westward flow of more than 2.2 million displaced people.
Tens of thousands of civilians fled cities including Sumy and Enerhodar on Wednesday, but evacuation routes elsewhere were too dangerous to use as Ukraine accused Russia of shelling civilian areas, including swathes of the besieged 400,000-strong port of Mariupol.
Footage from the city on the Azov Sea, which has been cut off without essential supplies for about a week, showed a maternity home and children's hospital in ruins and pregnant women being carried out stretchers. Local officials said at least 17 people were injured.
"Mariupol. Direct strike of Russian troops at the maternity hospital. People, children are under the wreckage. Atrocity!" tweeted Ukrainian president Volodymr Zelenskiy.
“How much longer will the world be an accomplice ignoring terror? Close the sky right now! Stop the killings! You have power but you seem to be losing humanity.”
Kremlin spokesman Dmitry Peskov said: "Russian forces do not fire on civilian targets."
The United Nations "has called for an immediate halt to attacks on healthcare, hospitals, healthcare workers, ambulances – none of these should ever, ever be a target", said UN spokesman Stephane Dujarric.
About 35,000 Ukrainians were evacuated through humanitarian corridors from three cities on Wednesday, Mr Zelenskiy said, adding that authorities planned to open another six escape routes on Thursday. He said the 35,000 civilians had left from the cities of Sumy and Energodar as well as towns in the Kyiv region.
British prime minister Boris Johnson said "there are few things more depraved than targeting the vulnerable and defenceless" and said the UK would hold Russian president Vladimir Putin to account "for his terrible crimes".
Britain's defence secretary, Ben Wallace, said London planned to supply Ukraine with Starstreak missiles, which it believes "will remain within the definition of defensive weapons but will allow the Ukrainian force to better defend their skies".
Nato has rebuffed Ukraine's requests for a no-fly zone over the country, amid concerns that it could cause a direct clash between the western alliance and Russia.
Those fears are also dogging a proposal to send Polish MiG-29 fighter jets to the Ukrainian air force, after Warsaw offered to transfer the planes via a US base in Germany.
"Departing from a US Nato base in Germany to fly into airspace contested with Russia over Ukraine raises some serious concerns for the entire Nato alliance… It's simply not clear to us that there's a substantive rationale for doing it in [this] way," said US secretary of state Antony Blinken.
Ukraine warned of a potential radiation leak at the Chernobyl nuclear power station after its electricity supply was cut off, but the International Atomic Energy Agency said it saw "no critical impact on safety".
The EU added fresh sanctions to the West’s vast array of punitive financial measures against Russia on Wednesday, but the Kremlin has vowed to continue its war on Ukraine, even as Mr Zelenskiy suggested he may be open to “compromises” with Moscow.
EU leaders will meet on Thursday for an informal summit in Versailles near Paris, which is expected to be dominated by discussions on the invasion of Ukraine, and its implications for the EU.
The leaders are likely to discuss the EU’s response to the refugee crisis, how to rapidly eliminate Europe’s dependence on Russian gas imports, as well as the security threats posed by the invasion. Additional reporting: Reuters