The City Hall in Donetsk in eastern Ukraine says at least 3 people have been killed in shelling overnight.

This follows artillery strikes on the rebel stronghold on Wednesday which hit a hospital, leaving five people dead.

Fighting between Russia-backed separatists and government forces picked up in January after a month of relative calm. The rebels pledge to carry on with their offensive on the government positions until Kiev stops shelling cities like Donetsk.

The Ukrainian government is anxious to use Thursday's visit by U.S. Secretary of State John Kerry to Kiev to reiterate its plea for lethal aid. President Barack Obama has opposed the idea of sending weapons to Ukraine but sources in his administration say this position could change in the light of recent events.