"The Russian invaders launched a missile attack on Kyiv region" at about 4:00 am local time (0200 GMT), Ukraine's air force said, adding that "air defence destroyed eight air targets that were flying in the direction of the capital".

Missile fragments fell in the eastern Darnytskyi district of the city, injuring four people, according to the military administration.

"Medics provided them with help on the spot," said Kyiv mayor Vitali Klitschko in a Telegram post.

"Also, a missile fragment was found on the territory of a warehouse in Darnytskyi district. There was no fire or damage to the building."

Ukrainian authorities accuse Russia of preparing a campaign of strikes on the country's energy infrastructure in the middle of winter, as it did last year.

During the winter of 2022, such strikes left millions of people without power for long periods during a cold snap.

Kyiv has since reinforced its air defence systems with weapons from its European and US allies, but says more is needed to protect vulnerable regions.