The Ukrainian military says six of its soldiers have been killed and 14 wounded in the past 24 hours in the separatist east of the country despite the current ceasefire.

The situation is particularly tense around the airport near the city of Donetsk, which is controlled by the rebels, the military spokesman Andriy Lysenko said.

“The enemy threw tanks, armoured personnel carriers and heavy artillery into battle. We emphasise that rebels are also firing at residential areas,” he said.

The casualties were the result of landmine explosions and shelling by the pro-Russia separatists, he added.

The truce brokered by the leaders of Ukraine, Russia, Germany and France is in its fourth month and has stemmed large-scale fighting, but skirmishes claim lives on both sides on an almost daily basis, and international monitors have warned of the threat of a bigger flare-up.

Separatist officials accused Ukrainian forces of firing at the village of Oktyabrsky, near Donetsk, wounding two civilians, and shelling three districts of the city over the last day, according to the rebel DAN press service.

At least seven people, including five civilians, were reported killed on Thursday, and more than 35 died last week in exchanges of mortar and rocket fire across the buffer zone established by the February truce.

The Organisation for Security and Cooperation in Europe said on Thursday that despite assertions to the contrary, neither side has completed the withdrawal of heavy weaponry as agreed in the ceasefire deal.

The UN estimates that at least 6,400 people have been killed in the conflict and more than a million have been forced to flee their homes.