KIEV (AFP) - Both sides in Ukraine's conflict have agreed to pull back their heavy weapons from the frontline in accordance with a United Nations-backed truce, a Ukrainian military official told AFP on Sunday.

"The papers have been signed to begin withdrawing heavy weapons all along the frontline," General Olexander Rozmaznin said.

The rebels confirmed separately through their own news agency that they had also signed the agreement.

Gen Rozmaznin said it was too early to say when the arms pullback would start. Some Ukrainian media suggested it could begin later on Sunday.

Under the terms of the truce, mediated by Germany and France and put into effect a week ago, the withdrawal of the weapons was meant to have started on Tuesday and be completed by March 3.

But up to now, that truce has been repeatedly violated. The rebels notably ignored it to overrun Ukrainian troops in the strategic eastern town of Debaltseve.

However in another sign that both sides in the conflict might now be willing to apply the truce, an overnight prisoner exchange took place in which 139 Ukrainian soldiers were traded for 52 rebel fighters.