Nine civilians have been killed in new fighting between government forces and pro-Russian separatists around the cities of Luhansk and Donetsk in east Ukraine, local officials said.
Six people were killed in shelling and gunfire on the outskirts of Donetsk, deputy mayor Kostantyn Savinov said.
City officials said three were killed in shelling of Luhansk over the previous 24 hours.
A Reuters reporter in central Donetsk said the shelling echoed through the night and witnesses said several buildings caught fire in the outlying Petrovsky district, including a school.
The smell of smoke stretched as far as the city centre.
Many residents of Luhansk, which is close to the border with Russia, have no electricity and some are without water, the city administration's press office said.
Advances by the Ukrainian army have forced the rebels out of most of the towns they had occupied in Russian-speaking east Ukraine.
They have mainly regrouped in Luhansk, which had a population of about 400,000 before the conflict, and Donetsk, which had about 1 million residents.
Pro-Russian separatists battled to keep advancing Ukrainian government forces at bay in heavy fighting on the outskirts of Donetsk.
Shelling by Ukrainian troops, some of them in sunflower fields outside the large industrial city, killed six people over the weekend.
The army is trying to tighten the noose around Donetsk.
The Ukrainian military said it had suffered no losses in the latest fighting.
Diplomatic efforts to end the conflict, in which in the United Nations says more than 1,100 people have been killed, have stalled.
The US and the EU have imposed sanctions on Russia.
It said it has not used its influence with the separatists to end the fighting.
Russia denies arming the rebels or orchestrating the conflict.
The fighting has intensified in east Ukraine since the downing of Malaysia Airlines flight MH17 in rebel-held territory on 17 July, killing 298 people.
Dutch and Australian forensic experts and police planned to continue recovery work at the site of the downed Malaysian airliner by examining debris in the village of Rozsypne, a few kilometres from the main wreckage.
The US says the separatists probably shot down the Boeing 777 by mistake with a Russian-supplied missile.
Moscow denies the accusation and blames the disaster on Kiev.
Roads to the crash site were for days too dangerous to use because of fighting.
Experts finally got there yesterday and hope to recover the last of the victims' remains.
The victims included 196 Dutch, 27 Australians and 43 Malaysians.
Shelling nearby forced the experts to stop their search for human remains today in one area where debris was found, but they were able to work unhindered at the main site.