Ukrainians have been bracing for weeks for an attack on the hobbled energy system, fearing crippling damage that would cause long blackouts as winter sets in and ramp up psychological pressure at a critical moment in the war launched by Russia in February 2022.

The strikes, which prompted emergency power cuts in numerous regions, came after this month's U.S. presidential election victory of Donald Trump, whose pledge to end the war without saying how has raised the prospect of a looming push to hold negotiations.

"Russia launched one of the largest air attacks: drones and missiles against peaceful cities, sleeping civilians, critical infrastructure," Ukrainian foreign minister Andrii Sybiha wrote on X.

Air defences could be heard engaging drones over the capital in the night, and a series of powerful blasts rang out across the city centre as the missile attack was under way in the morning.

Kyiv's air force said the military had destroyed 104 out of 120 missiles fired and 42 out of 90 drones launched by Russia.

Russia's defence ministry said it had launched a massive strike on energy facilities that supply Ukraine's military-industrial complex.

"Severe damage to Ukraine's energy system, including to DTEK power stations. These attacks again highlight Ukraine's need for additional air defence systems from our allies," said Maxim Timchenko, CEO of DTEK which is Ukraine's largest private energy provider.

After repeated Russian attacks on the power grid, officials reveal little about the state of the energy infrastructure and seldom release detailed information on the outcome of strikes.

Officials confirmed damage to "critical infrastructure" or reported power cuts in regions spanning from Volyn, Rivne, Lviv in the west to the southeastern Dnipropetrovsk and Zaporizhzhia regions. DTEK imposed emergency power cuts in the southern Odesa region at the order of energy officials.

President Volodymyr Zelenskiy said the "massive combined attack targeted all regions of Ukraine".

In the southern Ukrainian city of Mykolaiv, two people were killed in an overnight drone attack, the governor said. Two people died and three were wounded in a strike on a rail depot in the central eastern Dnipropetrovsk region, rail authorities said.

In the western Lviv region, on the border with Poland, a woman in a car was killed, the governor said. Another two people were killed in the Odesa region.

In Kyiv, the roof of a residential building caught fire due to falling debris and at least two people were hurt, city officials said on the Telegram messaging app.

The huge wave of strikes took place as the war approaches this week's 1,000th day since Russia's full-scale invasion.

Russia last conducted a major missile strike on Kyiv on Aug. 26, when officials said it fired a salvo of more than 200 drones and missiles across the country, killing seven people.