Government forces in Ukraine and the pro-Russian separatists they have been battling for 10 months insist they are withdrawing heavy weapons from the frontline, as called for by a February ceasefire deal.

But confirming that the big guns are really being pulled back is proving difficult, creating frustration among residents trapped by the fighting.

"These weapons have to be withdrawn on both sides. I've lived through seven months of bombardments so I can tell you it's very important," Tamara Slivinskaya told AFP.

The 61-year-old was queueing for food aid on Lenin Square in Debaltseve, a strategic transport hub that fell to the rebels after the ceasefire was supposed to have taken effect.

"They say the rebels are withdrawing them and that the Ukrainians are doing nothing."

"As long as I haven't seen it with my own eyes, I don't know if it's true," Slivinskaya said, echoing the doubts that have shrouded reports of the arms withdrawal.

The European-brokered ceasefire deal signed in the Belarussian capital Minsk on February 12 calls for tanks and artillery to be withdrawn from a buffer zone of between 50 and 140 kilometres (around 30 to 90 miles).

Both sides initially dragged their feet, but now say the process is well under way as fighting abates in most areas.

Ukrainian military spokesman Anatoliy Stelmakh said Saturday that government forces had completed the first stage of the withdrawal, which calls for the pullback of guns with a calibre of 100 mm or more. "The second stage can commence as soon as we receive the order."

Alexander Zakharchenko, leader of the self-proclaimed Donetsk People's Republic, declared the separatists had already withdrawn 90 percent of their heavy weapons.

Kiev accused the separatists of merely shuffling the equipment around the frontline, or removing it only to smuggle it back into position after dark.

- OSCE demands inventory -

The Organization for Security and Cooperation in Europe (OSCE), which is tasked with monitoring the ceasefire, said Monday it was "not yet in a position to provide verification of withdrawals."

Doing so, said the monitoring mission, would require the parties to detail "where the weapons are based at the moment, on what routes they will be withdrawn, and the places the heavy weapons will be concentrated/stored."

For several days now, the OSCE has chronicled weapons movements.

On some days the account is very specific. On February 27, observers saw a convoy transporting five Grad multiple-launch rocket systems east of the city of Donetsk in the direction "away from the contact line".

In other cases, however, it was hard to say whether the weapons were being withdrawn -- or just relocated.

In the town of Ilovaisk, about 30 kilometres east of Donetsk, the OSCE said it saw "eight military-style trucks and three buses... moving south", without being able to provide further clarification.

Elsewhere, observers tracking two convoys of equipment near the second main rebel-held city of Lugansk were barred by the separatists from following them to their final destination.

- 'Delicate mission' -

"It's extremely delicate for these observers," an independent source in Donetsk, who is familiar with the OSCE's work but who did not wish to be identified, said.

"No-one knows them and suddenly you have to give them ultra-confidential information: the number, the location and the type of weapons you have. Every soldier fears falling foul of spies."

Journalists have also been unable to corroborate the parties' compliance with the accord.

Last week, the separatists showed the press what they presented as the withdrawal of 14 howitzers.

But the column of trucks that AFP saw towing the cannon away from the frontline, about 20 kilometres south of Donetsk, was later seen by other Western journalists doubling back a few hours later.