Three boys have been reported killed and another injured by a land mine in a separatist-controlled town in eastern Ukraine.

The separatist leaders in the Donetsk region said the explosion occurred on September 30 in the industrial frontline town of Horlivka, 30 kilometers north of the city of Donetsk.

The area has seen heavy fighting between the Russia-backed separatists and Ukrainian government forces.

Horlivka Mayor Ivan Prikhodko wrote in a social-media post that the dead were all aged between 13 and 15.

A fourth boy, aged 10, was injured in the explosion and was being treated in hospital for shrapnel injuries, he wrote.

Prikhodko told the AFP news agency that the group had gone for a walk, adding, “They found an abandoned house and were just looking for adventure."

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

More than 10,300 people have been killed since April 2014 in the war in eastern Ukraine, where separatists continue to hold parts of the Donestk and Luhansk provinces.

Peace accords signed in Belarus’s capital, Minsk, in September 2014 and February 2015, have failed to put an end to the fighting.

Based on reporting by Reuters and AFP