The announcement came a day after strikes on the city, which lies close to the Russian border, killing five people.

"At the current time in Kharkiv, three people have unfortunately died," regional governor Oleg Sinegubov said on Telegram.

He also told Ukraine's Hromadske television that 21 people were injured in the strikes Tuesday in four different residential areas.

"The intensity of the shelling of Kharkiv has increased," Sinegubov said, asking residents to take shelter and not go outside.

The governor of the eastern Donetsk region, Pavlo Kyrylenko, said later on Tuesday that three civilians were killed by Russian shelling: one in Kramatorsk, one in Avdiivka and the third in Blagodatnoye.

"Five civilians were also wounded, including a child," Kyrylenko said on Telegram.

Kharkiv, Ukraine's second city that had nearly 1.5 million inhabitants before Russia invaded in late February, saw heavy fighting at the start of Moscow's offensive but always remained under Ukrainian control.

Ukraine fears the city could be a major target in a new Russian offensive, which President Volodymyr Zelensky said had begun Monday.