"During the attack on Kyiv... a 62-year-old US citizen died in a house opposite to the place where medics were providing assistance to the injured," Vitali Klitschko said on Telegram.

Earlier he said 16 people had been wounded in the capital so far, most of them in Solomyansky district.

"Enemy UAVs are still heading towards the city from three directions. There is also a missile threat! Don't leave shelters!" Klitschko added.

Tymur Tkachenko, head of the Kyiv city military administration, said the capital was "currently under a combined enemy strike".

"The Russians are using missiles and strike drones. Fires in various areas," he added.

Ukrainian President Volodymyr Zelensky's chief of staff, Andriy Yermak, slammed the new Russian strikes on "residential buildings in Kyiv," saying on Telegram that Moscow was "continuing its war against civilians".

Moscow has kept up its attacks on Ukraine despite efforts by the United States to broker a ceasefire.

Talks have stalled. Moscow has rejected the "unconditional" truce demanded by Kyiv and its European allies, while Ukraine has dismissed Russia's demands as "ultimatums".