Ukrainian President Volodymyr Zelensky has called for stronger international sanctions on Russia after a deadly attack on Kyiv killed at least 31 people.

Zelensky said five children - the youngest aged two - were among the dead and 159 people - including 16 children - had been wounded in the assault on the Ukrainian capital on Thursday.

"No matter how much the Kremlin denies their effectiveness, sanctions do work - and they must be strengthened," he said.

Kyiv observed a day of mourning after the attack collapsed an apartment block and damaged a hospital, school, nursery and university.

Russia launched more than 300 drones and eight cruise missiles in Thursday's assault, Ukraine's air force said. The attack was one of the deadliest Kyiv has experienced since Russian President Vladimir Putin launched a large-scale invasion in February 2022.

US President Donald Trump condemned Russia's actions in Ukraine and suggested new sanctions against Moscow were coming.

"Russia, I think it's disgusting what they're doing. I think it's disgusting," he told journalists.

In July, Trump said Putin had 50 days to end the war, or Russia would face severe tariffs targeting its oil and other exports.

On Monday, Trump set a new "10 or 12" day deadline. He later set a new deadline, which would expire on 8 August.

Senior US diplomat John Kelley told the UN Security Council on Thursday that Russia and Ukraine "must negotiate a ceasefire and durable peace".

"It is time to make a deal," he said.

Ukrainian officials on Friday said Kyiv had received "positive signals" from the US about potential new sanctions, particularly targeting Russian oil and secondary markets.

Ukrainian Foreign Minister Andrii Sybiha said Trump has been "generous and patient", but that "now is the time to put maximum pressure on Moscow".

Meanwhile, Germany pledged on Friday to deliver two additional US-made Patriot air defence systems in the coming days.

Zelensky said in July alone, Russia launched more than 5,100 glide bombs, 3,800 Shahed drones, and 260 missiles, including 128 ballistic.

"Every day matters," he said. "This can only be stopped through joint efforts – by America, Europe, and other global actors."