Around 350,000 residents of Kharkiv and the surrounding region were left without electricity following an overnight Russian drone attack that also killed four people, including rescue workers.

"In Kharkiv and areas of the region, around 350,000 consumers have been disconnected," the Ukrenergo grid operator said in a statement. 

Russia has repeatedly struck Ukraine's electricity grid, cutting power to thousands of people in an attempt to damage its energy infrastructure. Last summer, Russian strikes blew up the Kakhova hydroelectric dam causing widespread flooding.

Commenting on Thursday's attack President Volodymyr Zelenskyy called it "despicable and cynical". 

"When the rescuers arrived at the scene of the strike, the terrorists attacked again." he said.