Both Ukrainian forces and Russian-backed rebels have pulled back most of their heavy artillery from the front line in accordance with a February ceasefire deal, Ukraine’s president said late Monday, amid reports of fresh clashes in the east.

Ukraine's President Petro Poroshenko told a state broadcaster that some heavy weaponry remains in place at the airport in the rebel-held city of Donetsk, however.

World leaders hope the withdrawal of heavy weapons as agreed at high-level peace talks last month will help bring a definitive end to the conflict, which the UN estimates has killed more than 6,000 people and displaced almost 1.8 million.

The pullback is being overseen by hundreds of monitors from the Organization for Security and Co-operation in Europe, or OSCE, which has in the past cited a lack of cooperation on both sides.

Poroshenko said in his interview that exchanges of artillery and rocket fire have largely stopped along the 485-kilometre (300-mile) front, but said skirmishes with small arms and grenade launchers persisted.

Under a February 12 peace deal concluded in the Belarusian capital of Minsk, heavy weapons are to be pulled back by between 25 and 70 kilometres (15 to 45 miles) from the front line, depending on their calibre.

But Ukrainian military spokesman Colonel Andriy Lysenko said Tuesday that pro-Russian rebels were amassing heavy weapons in depots around the separatist-held city of Donetsk despite the ceasefire deal.

"[Rebels] are continuing to transport equipment and artillery ammunition intensively via the Debaltseve railway junction and build weapons storages around Donetsk," Lysenko said in a televised briefing.

Rebels consolidated their hold on Delbaltseve in the days after the ceasefire came into effect as Ukrainian forces withdrew from the city.

Pitched battles are also taking place in the town of Shyrokyne near the strategic port city of Mariupol, which Kiev fears could be the focus of the next rebel offensive. Mariupol lies on the coast of the Sea of Azov between rebel-held areas of east Ukraine and Crimea, which was annexed by Russia in March of last year.

Lysenko said the fighting in Shyrokyne raged for more than three hours on Monday. He said Ukrainian positions had come under attack from separatists 31 times, including five instances of artillery fire, and that nine servicemen had been wounded in the past 24 hours.

Rebel representatives said Ukrainian forces had themselves violated the ceasefire 17 times in the same period but reported no casualties.

(FRANCE 24)