Ukraine's army on Sunday accused Russian forces of shooting two prisoners of war and posted a grainy video shot from the air that they said showed the incident.
In the video, two soldiers labelled as Ukrainians run towards another labelled as Russian in a trench.
The Russian soldier then grabs them and shoots numerous times until they stop moving, before turning back. The two men do not appear to have resisted capture.
AFP could not verify the authenticity of the video or the location.
"This morning... the Russians once again showed their attitude to international humanitarian law by shooting two Ukrainian prisoners of war," the ground forces wrote on Telegram.
They said the incident happened in the area of responsibility of the Khortytsia group of troops, which operates on the eastern front, without giving a more precise location.
Ukrainian media reported it happened northeast of the village of Vesele in the Donetsk region, citing the Khortytsia group's press service.
Khortytsia's troops were not involved in the withdrawal from the town of Avdiivka in the region, which Russia claimed Saturday to fully control.
Russia and Ukraine have several times accused each other of violating international humanitarian law by killing prisoners-of-war since Russia invaded.
The United Nations Human Rights Office of the High Commissioner has documented cases of summary executions of Ukrainian prisoners of war as well as torture.
Earlier Sunday, the DeepState Telegram channel seen as close to the Ukrainian army reported that Russian forces had shot six injured Ukrainian soldiers left behind during the withdrawal from Avdiivka, most likely on Thursday.
It said the men had been too badly wounded to leave the Zenit position near the town of Avdiivka with other troops during Ukraine's withdrawal and comrades had recognised their bodies on a video posted on social media by Russians.
Ukrainian authorities have not commented on this report.