A Ukrainian military spokesman says more than 90 percent of its forces have been withdrawn from the fiercely contested town of Debaltseve and its surroundings, but left unclear when the retreat might be completed.

Ukrainian forces began abandoning Debaltseve on Wednesday after weeks of heavy fighting against Russia-backed separatists. Control of the town is a significant strategic gain for the rebels because it is a railway junction and straddles the most direct route between Donetsk and Luhansk, the separatist region's two major cities.

The battle for Debaltseve had continued to rage despite a cease-fire that was called into effect on Sunday.

Military spokesman Anatoliy Stelmakh also said Thursday that rebels heavily shelled a village on the outskirts of the port city of Mariupol during the last day.