Hundreds of thousands of people across Ukraine were left without electricity after Russian strikes targeted the country's energy infrastructure overnight, Ukrainian authorities and energy officials said on Sunday.

In the central Dnipropetrovsk region, power company DTEK said on Telegram that "more than 600,000 residents of the region have been left without power" following what it described as a night attack that damaged important energy facilities.

The company said it was working to restore electricity supplies to affected households, but cautioned that the repair effort was "complicated by repeated attacks" on the power grid.

The overnight strikes came a day after Ukraine's energy ministry said a massive attack on energy facilities had plunged residents in five regions into darkness and significantly hampered electricity transmission in the capital, Kyiv.

In a separate strike, a Russian drone hit what was described as "a critical infrastructure facility" in the northeastern Kharkiv region, according to Mykola Baksheyev, the mayor of the city of Zlatopil. "Nearly 250,000 customers in the Kharkiv region were left without power," Baksheyev said on social media.

Ukrainian President Volodymyr Zelenskyy said the night-time strikes had triggered "widespread power outages across the country." Zelenskyy has previously accused Russia of ramping up its attacks on Ukraine ahead of trilateral talks with Moscow that are expected next week.

"In the Zhytomyr region alone, 140 apartment buildings were left without heating following a Russian strike," Zelenskyy said, as temperatures across Ukraine already hovered around freezing.

Zelenskyy also said Russia had launched a drone at Komyshuvakha, a village in the Zaporizhzhia region where Moscow hit an aid distribution centre on Monday in one of the deadliest attacks of the war. The death toll from that strike has risen to 55 people, Zelenskyy said, after emergency services had previously reported that 50 were killed.

"This morning, the Russians attacked Komyshuvakha with an FPV drone, where emergency rescue operations have been underway for seven days .. Unfortunately, more people may still be under the rubble," Zelenskyy said.