Dorji Batomunkuev, military unit number 46108, is 20 years old and part of the Russian fifth tank brigade from Ulan-Ude, a city near the Mongolian border. He is a conscript and was called up 18 months ago. When we meet at the Central Regional hospital in Donetsk, his face and hands are burnt and bandaged, and his ears are singed and shrivelled. Beneath the dressings, he's still bleeding.

He says he was injured in the eastern Ukraine town of Lohvynove on 9 February, at the mouth of the Debaltseve pocket, while fighting alongside the separatist militia of the Donetsk People's Republic against Ukrainian forces.

Russia has denied that its forces are fighting in Ukraine, although a recent report by the Royal United Services Institute contests this, suggesting that several units have crossed the border since the conflict began. At their peak in December 2014, they numbered some 10,000 troops, the report says.