Artillery has killed at least four people in a residential area in eastern Ukraine, spurring more people to flee the besieged city of Donetsk and its suburbs.

Pro-Russian insurgents last week retreated from the strategic city of Sloviansk and holed up in Donetsk. The overnight artillery strike in Maryinka, a western suburb of Donetsk, hit four apartment blocks near a rebel base. It was unclear which side fired at the buildings.

Fighting between the rebels and government troops has left more than 400 dead and tens of thousands have fled their homes.