Russian missiles and drones tore through apartment buildings in the Ukrainian capital of Kyiv, killing at least 15 people, including four children.
The attack, according to President Volodymyr Zelensky, shows Moscow's rejection of peace talks.
Russia continues to launch air strikes on Ukrainian cities, despite calls from US President Donald Trump for a ceasefire and even as he talks about the importance of ending the war that began with its full-scale invasion in February 2022.
The attack, one of the deadliest in Kyiv, blew a five-story hole in an apartment building, tearing the structure in two.
AFP reporters saw rescuers carrying victims away in body bags as they searched through the smoldering rubble.
Heavy construction machinery was used to clear away the piles of debris. Officials warned that several people were believed to still be trapped under the collapsed building.
"Glass was flying... we were screaming when the bombs exploded," said Galina Shcherbak, who was in a parking lot near one of the strike sites.
The Ukrainian Air Force said Moscow had fired 629 drones and missiles. According to an AFP analysis of data from Kyiv, this makes it the second-largest bombardment overnight since the start of the war.
Zelensky called the attack "a horrific and deliberate killing of civilians."
"The Russians are not choosing to end the war, only new strikes," he said on social media, calling on Moscow to face new sanctions.
"New strong sanctions are needed for Russia's rejection of the truce and its constant attempts to wriggle out of negotiations," he added.
"All deadlines have already been violated, dozens of opportunities for diplomacy have been wasted. Russia must feel responsible for every strike, for every day of this war," the Ukrainian head of state said.
The Kremlin, which claims to have targeted military sites, insists that it is still interested in diplomacy, but that its strikes against Ukraine will "continue."
"The Russian armed forces are carrying out their tasks," said Kremlin spokesman Dmitry Peskov.
"They continue to strike military and military-related infrastructure facilities. At the same time, Russia remains interested in continuing the negotiation process. The goal is to achieve our objectives through political and diplomatic means," he added.
The EU summoned the Russian ambassador after overnight strikes damaged its delegation's offices in Kyiv.
EU officials posted photos of broken windows and a partially collapsed ceiling in the office.
The British Council also said its premises had been "seriously damaged" and would be closed until further notice.
British Prime Minister Keir Starmer accused Russian President Vladimir Putin of "sabotaging hopes for peace" with the strikes.
French President Emmanuel Macron condemned Russia's "terror and barbarism."
"This is Russia's idea of peace," he said in a post on X.
Following the summit between Russian President Vladimir Putin and Trump in Alaska earlier this month, the Kremlin rejected initiatives for a rapid end to the fighting, including pressure for a meeting between Zelensky and Putin.
Moscow is demanding that Kyiv cede more territory and renounce Western military support as conditions for any peace agreement — ultimatums that Kyiv rejects.
Putin has rejected repeated calls for a cease-fire from Zelensky, Trump, and European leaders.
Ukraine has long accused Russia of only paying lip service to the idea of stopping the invasion.
Russian forces said they had captured another small village in the eastern Donetsk region, the latest in a series of grueling and costly offensives.
Before signing any peace deal, Ukraine wants security guarantees, including the deployment of Western troops to deter future Russian attacks.
Moscow has opposed the prospect of Western military forces in Ukraine.
Meanwhile, Kyiv said it had struck two large refineries in Russia in its overnight attacks, which it called just retaliation. | BGNES