The French president says he and German Chancellor Angela Merkel have spoken with the leaders of Ukraine and Russia about the cease-fire that has been faltering amid fierce fighting over the eastern town of Debaltseve.

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 the separatist region's two major cities.

The battle for Debaltseve had continued to rage despite a cease-fire that came into effect Sunday in eastern Ukraine. French President Francois Hollande says the phone call Thursday morning touched upon cease-fire violations and their consequences.