The withdrawal of heavy weapons on both sides of the conflict in eastern Ukraine should begin in earnest on Tuesday, German Chancellor Angela Merkel's spokesman confirmed after the chancellor spoke on the telephone with her Ukrainian and Russian counterparts.

The Chancellor's conversation with Petro Poroshenko and Vladimir Putin resulted in "concrete steps" towards the removal of weapons and enabling the Organization for Security and Cooperation in Europe (OSCE) to observe the ceasefire, said Merkel spokesman Steffen Seibert.

One of the most important topics of conversation was the situation in Debaltseve, where around 8,000 Ukrainian soldiers are said to be surrounded by pro-Russian separatist forces who refuse to let them leave with their weapons.

Merkel and Poroshenko asked Putin to "exert his influence on the separatists, in order to put out this fire" and allow the OSCE observers free entry into the conflict zone, which they say they have been barred from until now, despite the truce agreement reached last week in the Belarusian capital Minsk.

"Moral" obligation to continue fighting

Both sides have accused the other of breaking the ceasefire, especially around Debaltseve, an important junction between the rebel strongholds of Luhansk and Donetsk, though the agreement appears to mostly be holding in other areas.

The Ukrainian government and rebel troops now have two weeks to remove tanks and artillery to a 50-140 kilometer (37-81 mile) wide "safety zone." However, some rebel leaders told Reuters new agency that they cannot "morally" halt fighting in Debaltseve, as they consider it "internal territory."

"We have to respond to fire, to work on destroying the enemy's fighting positions ... We are ready at any time (to start the removal of heavy weapons), we have everything ready for a mutual withdrawal. We will not do anything unilaterally -that would make our soldiers targets," rebel spokesman Denis Pushilin said to Reuters.

es/ (AFP, dpa, Reuters)