A suburb of the rebel-held Ukrainian city of Donetsk has come under heavy bombardment, a day after the army suffered some of its heaviest losses.

Apartment blocks were hit as shelling continued through the night and into Saturday in Marinka, west of the city.

Pro-Russian rebels said 30 civilians had been killed by government shelling, but the death toll could not be verified independently.

On Friday, a rebel attack in Luhansk region killed at least 19 soldiers.

President Petro Poroshenko vowed to retaliate, saying: "For every soldier's life, the militants will pay with tens and hundreds of their own."

The rebels, who declared independence in Donetsk and Luhansk in April, retreated towards the city of Donetsk last week after a government siege of their symbolic stronghold, Sloviansk.

More than 1,000 civilians and combatants are believed to have died in the fighting since April.