Donetsk (Ukraine) (AFP) - One person was killed and three others wounded Saturday as fresh clashes erupted in eastern Ukraine's rebel bastion of Donetsk, violating a ceasefire that had been holding for several weeks, separatist and loyalist sources said.

It was the first serious incident in the flashpoint area since an early September truce agreement, and underscored the fragility of the internationally-backed peace process between the warring parties.

According to the pro-Moscow rebels, Ukrainian army fire killed one fighter and wounded two others near an airport smashed by months of fighting in the outskirts of separatist "capital" Donetsk.

AFP journalists saw an abandoned residential building near the airport on fire after being struck by a round.

Bursts of what was likely light artillery could be heard as night fell.

The Ukrainian army denied responsibility for the casualties claimed by the separatists and instead blamed its foe for the unrest, in which it said one soldier was wounded.

"We came under heavy machine-gun and grenade-launcher fire" from the airport, army spokesman Oleksandr Zavtonov told AFP.

"We retaliated using firearms so that we could evacuate a wounded person, but those forbidden (by a fragile peace deal) were not used," he added.

Rebel military leader Eduard Basurin told AFP the three casualties on his side were all fighters.

In a statement, the Ukrainian military chief of staff blamed the rebels' "provocations".

"Unlike the insurgents... Ukrainian forces fully respect the Minsk (peace) accords," the statement said.

The rebels initially said they had been targeted with tank rounds, though they later said they had been hit using 120 mm mortars. Both types of weaponry have been banned under the so-called Minsk II agreement that was signed in February.





- 'Maximum restraint' -





Under the deal, eastern Ukraine is supposed to hold local elections by the end of the year and hand back control of the Russian border to the government in Kiev.

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The Organisation for Security and Cooperation in Europe (OSCE), whose observers are deployed in eastern Ukraine, confirmed the death of a "presumed" rebel, adding that there may have been other casualties.

Ertugrul Apakan, who heads the observers' mission, voiced concern over the sudden escalation.

"People are looking for peace, tranquility and stability," Apakan said.

"There's no rationale for what happened. I call upon all parties to exercise maximum restraint."

The conflict in eastern Ukraine has killed more than 8,000 people since it broke out in April 2014. Violence in the area has been extremely rare since the early September truce agreement.

In line with the ongoing peace process, the warring parties claim they have withdrawn all heavy weapons of a calibre higher than 100 mm from the frontline, but the OSCE says neither side has yet fully pulled out its arms.

The smaller arms withdrawal began in the nearby rebel region of Lugansk in early October and continued Saturday. The process has not yet begun in Donetsk however.

Speaking just hours before Saturday's incident, Ukrainian President Petro Poroshenko had warned that peace was still far off.

"I want to remind everyone: the war isn't over yet. And the end is still far off," he said in a speech in Kiev.

Ukraine's security service SBU chief Vassyl Grytsak on Saturday said 6,000 to 9,000 Russian soldiers were still deployed in eastern Ukraine.