The United Nations said Friday it was "deeply concerned" by what it described as summary executions of prisoners of war carried out by Russian and Ukrainian forces on the battlefield.
The head of the UN Human Rights Monitoring Mission in Ukraine, Matilda Bogner, said her organisation had documented killings, often on the battlefield, by both sides in recent months.
"We are deeply concerned about summary execution of up to 25 Russian prisoners of war and persons hors de combat by the Ukrainian armed forces, which we have documented," Bogner said at a press conference in Kyiv.
"This was often perpetrated immediately upon capture on the battlefield. While we are aware of ongoing investigations by Ukraine authorities into five cases involving 22 victims, we are not aware of any prosecution of the perpetrators," she added.
Bogner also related the UN's "deep" concern over "the summary execution of 15 Ukrainian prisoners of war shortly after being captured by Russian armed forces".
She said the Wagner mercenary group, which claims to be leading Russia's assault for Bakhmut, the longest and bloodiest battle of the war, was responsible for some 11 of those killings.
Ukraine and Russia have both accused each other of mistreating prisoners of war since Russian President Vladimir Putin invaded a year ago.