Ukraine’s president, Volodymyr Zelenskiy called the Russian strike on a maternity hospital in Mariupol “the ultimate evidence of genocide”. The children’s hospital and maternity ward in the southern Ukrainian city was destroyed by a Russian airstrike on Wednesday afternoon, Ukrainian officials said. Zelenskiy said children are buried under rubble and the regional governor said 17 people have been wounded. “A children’s hospital, a maternity ward. How did they threaten the Russian Federation?” Zelenskiy added. The Guardian was unable to fully verify Ukrainian officials’ accounts, but video published by the Associated Press showed multiple injured people at the site of the hospital attack.

Western officials warned of their “serious concern” that Vladimir Putin could use chemical weapons on Kyiv. In an assessment, they said an “utterly horrific” attack on the Ukrainian capital could be unleashed as Russian forces attempt to overcome the logistical issues that have apparently plagued troops headed towards Kyiv.

Britain is planning to supply Starstreak anti-aircraft weapons and “a small consignment” of Javelin anti-tank missiles to Ukraine as Russian forces close in on Kyiv, the British defence secretary has said.

Russian foreign minister Sergei Lavrov has landed in Turkey for the face-to-face talks on Thursday with his Ukrainian counterpart Dmytro Kuleba, the highest-level meeting between the two countries since Russia invaded. Kuleba warned in a Facebook video his expectations were “limited”. So far, the parties have been engaged in lower-level talks in Belarus, largely over humanitarian issues and involving only Ukrainian officials.

Leaders of the 27-nation EU are to meet in Versailles on Thursday and Friday. A draft declaration prepared for the summit said: “Russia’s war of aggression constitutes a tectonic shift in European history.” The leaders are expected to discuss reducing the bloc’s energy dependency on Russia, and Ukraine’s request to join the EU.

Russia’s foreign ministry has confirmed the use of the TOS-1A weapon system in Ukraine, Britain said. The UK’s ministry of defence said the system uses thermobaric rockets, creating incendiary and blast effects. Here is an explainer on thermobaric weapons.

The United States has seen indications that Russia is dropping “dumb bombs” – unguided munitions with no precise target – on Ukraine, a senior US defence official said. Officials added that the US was observing “increasing damage to civilian infrastructure and civilian casualties”.

Ukraine has accused Russian forces of “holding 400,000 people hostage” in Mariupol. The Ukrainian foreign minister, Dmytro Kuleba, said the city, where conditions are described as “apocalyptic”, was still being shelled by Russian troops despite an agreement to establish a safe evacuation corridor for civilians.

Ukrainian authorities have said the power supply has been cut to the defunct Chernobyl power plant. The UN’s atomic watchdog said the spent nuclear fuel stored there had cooled down sufficiently for it not to be an imminent concern. Still, the news is raising concerns that a lack of external power to the site could compromise nuclear safety.

More than 40,000 civilians were evacuated from across Ukraine on Weednesday but authorities struggled to get people away from conflict zones around the cities of Kyiv, Kharkiv and Mariupol, a Ukrainian negotiator said. Ukrainian authorities said earlier that the corridors should allow residents of the heavily bombarded cities of Mariupol, Enerhodar, Sumy, Izyum and Volnovakha, as well as towns around Kyiv including Bucha, Irpin and Hostomel, to leave, calling on Russian forces to respect an “official public commitment” to cease fire.