North Korean troops have not been seen on the frontlines in Russia’s Kursk region for several weeks, a Ukrainian military official said Friday, amid reports of mass casualties among Pyongyang’s forces.

The soldiers appear to have been pulled back from the front lines in Kursk after suffering heavy casualties during barely a month of combat, Ukrainian officials said.

North Korean troops have been pulled back from the frontline amid devastating losses, according to Ukrainian and American officials. Kim Jong Un ’s forces have not been seen on the battlefield for around three weeks, Ukrainian special forces said, according to the New York Times.