Pro-Russian separatists in eastern Ukraine claimed Saturday to have fulfilled their end of a February deal with government forces to withdraw heavy weapons from the frontline as part of a cease-fire.

"Today is the last day of the weapons withdrawal," Eduard Basurin, one of the rebel leaders, told reporters in the town of Snizhne, where the separatists displayed eight 120mm mortars that had been moved back from their positions.

However, Ukraine said on Sunday that one soldier has been killed in the country's east by pro-Russia separatists but that the EU-mediated cease-fire was largely being observed.

"One soldier died and three were injured" since Saturday, said security spokesman Andriy Lysenko in a briefing in Kiev. "However the Minsk accords are largely being fulfilled," he said, "the number of attacks has gone down considerably over the past day."

Watched by six international monitors, who declined requests for comment, the separatists towed the arms to a disused brick factory serving as an arms depot, about 90 kilometers from the rebel hub of Donetsk.

Basurin said the separatists were withdrawing a total of 26 mortars. "They will be stored with the rest of the military hardware," he said.

An AFP journalist saw four other artillery pieces inside the Snizhne depot.

Under the terms of the European-brokered, Russian-backed truce signed in the Belarussian capital Minsk on February 12, both sides to Ukraine's 11-month conflict must move their artillery back far enough to create a buffer zone of between 50 and 140 kilometers, depending on the weapons' range.

The process has been fraught with distrust and mutual recriminations, with both parties accusing the other of merely paying lip service to the peace deal.

Beyond the heavy weapons, the deal also calls for the withdrawal "of all foreign armed formations" and military equipment from Ukrainian territory - an allusion to the accusations by Kiev and the West that Russia is arming and manning the conflict on the rebel side.

The accord also commits Kiev and the rebels to exchange all prisoners and to negotiate a change to Ukraine's constitution by the end of 2015, in order to give rebel-held areas more autonomy.

On Saturday they again traded accusations of violating the cease-fire in the past 24 hours.

Separately, the European Commission chief Jean-Claude Juncker on Sunday called for the creation of an EU army in the wake of rising tensions with Russia.

Juncker said the force could help counter new threats beyond the bloc's borders and defend European "values" in an interview with Germany's Welt am Sonntag newspaper.