At least four people have been killed and more than 60 people injured after Russia unleashed 'the most powerful attack' since the start of the war with Ukraine, officials said on Saturday.

Drones, missiles and guided bombs pelted down on the eastern Ukrainian city of Kharkiv during the overnight assault, with the injured said to include a baby.

One of Ukraine's largest cities, Kharkiv is located just a few dozen kilometres from the Russian border and has been under constant Russian shelling during more than three years of war.

'Kharkiv is currently experiencing the most powerful attack since the start of the full-scale war,' city mayor, Ihor Terekhov, said on Telegram on Saturday.

Dozens of explosions were heard in the city throughout Friday night and Russian troops were striking simultaneously with missiles, drones and guided aerial bombs, he said.