Hundreds of thousands of children are at imminent risk of being hit by mines and other explosive weapons in war-torn eastern Ukraine, one of the most mine-contaminated places on earth, a UN report said Thursday.

A bloody conflict between Ukraine's army and Russian-backed rebels has endangered 220,000 children who live, play and go to and from school in areas littered with landmines and other deadly explosive devices, the UN International Children's Emergency Fund (UNICEF) said.

"It is unacceptable that places where children could safely play less than four years ago are now riddled with deadly explosives," said Giovanna Barberis, the agency's Ukraine representative.

"All parties to the conflict must immediately end the use of these gruesome weapons that have contaminated communities and put children in constant danger of injury and death."