Russia's artillery fire hit a school early Thursday as well as a cultural centre in the town of Merefa outside the city of Kharkiv.

Of the injured, 10 people are in serious condition, said reports.

The shelling left several storeys of a building destroyed and emergency workers were seen combing through the wreckage to evacuate anyone stuck.

Kharkiv, Ukraine's second-largest city, has been one of the hard-hit areas which came under intense Russian airstrikes in recent weeks. The city has been left severely damaged.