France's foreign minister said the attack on the Kyiv Pechersk Lavra monastery, a UNESCO World Heritage site founded in 1051, was akin to bombing Notre Dame cathedral in Paris.
The Russian strikes came after Ukraine's President Volodymyr Zelenskiy said on Sunday he had discussed with US President Donald Trump efforts to secure an end to the more than four-year conflict, ahead of a G7 meeting in France this week.
"A Russian strike on the Kyiv-Pechersk Lavra set the Dormition Cathedral on fire - a church whose history dates back to the 11th century. And this is one of Russia's most serious crimes against Christian culture to date," Zelenskiy said on X.
"This is an attack on our history," he said later, while visiting the damaged monastery and adding, "Of course everything will be restored."
As flames leapt above the religious compound, Kyiv residents took shelter underground in the worst Russian attack on Ukraine since early June, when drones and missiles killed more than 20 people and left more than 100 wounded.
Russia denied striking the monastery and said it had been damaged by a US-made Patriot air defence missile but Zelenskiy said during a visit to the site that it had been struck by a Russian drone.
A source familiar with the situation provided Reuters with a photo of what he said were Russian drone debris found near the damaged cathedral building in the Lavra.
Reuters was not immediately able to confirm the authenticity of the image.
"What more must the Kremlin Antichrist do for the world to realise that decisive action must be taken so that the Russian terror against Ukraine and the very principles of peace come to an end?" Metropolitan Epifaniy, head of the Orthodox Church of Ukraine, said in a social media post.
Four people were killed and 34 were injured in the overnight strikes on Kyiv, said Tymur Tkachenko, the head of the capital's military administration. Kyiv's Mayor Vitaliy Klitschko later said a fifth person had died in hospital from their injuries.
A Russian strike on Kharkiv, Ukraine's second-largest city, killed four emergency service rescuers and a municipal official and injured at least five other people, Interior Minister Ihor Klymenko said on Telegram.
Three people, including a child, were also wounded in the northeastern city of Sumy, local authorities said in social media posts.
Meanwhile,a Ukrainian drone attack on the Russian city of Tula, an industrial cluster south of Moscow, killed three people and three others, including a one-year-old child, the regional governor said in a Telegram post.
Russia and Ukraine both deny deliberately attacking civilians. Reuters could not independently confirm the reports.
Ukraine's military said Russia had launched 70 missiles and 611 drones against Ukraine overnight and that its air defences had shot down 50 missiles and 582 drones of various types.
Neighbouring Poland, an EU and NATO member, scrambled fighter jets on Monday against a possible airspace incursion, before recalling the alert and saying no sky violation had been recorded, its Armed Forces said in a post on X.
European leaders condemned the attack on the Kyiv monastery.
"This is a UNESCO world heritage site, which for us in France is the equivalent of Notre Dame or Saint Denis being bombed," said French Foreign Minister Jean-Noel Barrot.
The EU's foreign policy chief Kaja Kallas called the attack a "war crime". French President Emmanuel Macron said G7 leaders meeting in France would discuss how to end the war in Ukraine.
with DPA
