Mortar fire struck an apartment block in the city of Donetsk overnight, yet another violation of a cease-fire declared weeks earlier between government forces and pro-Russian separatists.
The attack came even as both sides claimed to be pulling back heavy artillery to set up a buffer zone.
More than 3,000 people have been killed in the conflict since mid-April with key infrastructure such as airports and bridges completely destroyed by shelling.
The Donetsk mayor’s office on Wednesday reported two attacks, one late on Tuesday and another in the early hours Wednesday. In one of them, a mortar shell hit an apartment block.
The RIA Novosti news agency quoted the rebels as saying that two people died in the attack but the mayor’s office had no information about casualties.
The cease-fire between the rebels and Ukrainian troops has largely held since both parties agreed to it on Sept. 5, despite sporadic artillery attacks and casualties.
At talks last weekend, both sides agreed to pull back heavy artillery, setting up a buffer zone. Separatists said on Wednesday they were implementing this agreement as well as the Ukrainians.
The West and Ukraine have accused Moscow of propping up the rebels with arms and volunteers from the onset of the conflict. NATO has also reported Russian troops fighting on the Ukrainian territory.
Canadian Lt. Col. Jay Janzen, a NATO military spokesman, told The Associated Press on Wednesday that NATO has witnessed “a significant pullback of Russian conventional forces from inside Ukraine,” but added that “some Russian troops still remain.” He said it was difficult to say how many were still in Ukraine because they were moving across the border which is largely controlled by the separatists.