KIEV (AFP) - Three children were killed and another injured Sunday (Sept 30) by a landmine blast in rebel-held eastern Ukraine, which remains littered with explosives left behind during a four-year war.

The explosion happened in the industrial frontline city of Gorlivka, 30km north of the rebel area's de facto capital Donetsk, separatist "defence minister" Eduard Basurin told AFP.

The wounded child, who was 10, was hospitalised, he added.

Gorlivka mayor Ivan Prikhodko told AFP the children had gone for a walk.

"They found an abandoned house and were just looking for adventure," he said.

"We are constantly confronted (by the problem of mines) and I think it is something that will continue for some time," he added.

The blast was the latest in a string of deadly explosions to hit the unrecognised Russian-backed republic over the past few weeks.

On Saturday (Sept 29), three people were injured in an explosion in Donetsk, including a candidate for the post of the self-proclaimed republic's leader.

In August, the head of the Donetsk People's Republic, Alexander Zakharchenko died in a daylight bombing at a cafe.

More than 10,000 people have been killed since the rebel insurgency broke out in the eastern Donetsk and Lugansk regions in April 2014 following Russia's annexation of Crimea from Ukraine.

Ukraine and its Western allies have accused Russia of funnelling troops and arms across the border, but Moscow has denied the claims despite overwhelming evidence to the contrary.

A series of truce agreements have helped to reduce the fighting, although sporadic clashes continue and both military personnel and civilians face a constant threat from landmines.