Kyiv accused Russia on Saturday of committing a war crime by executing Ukrainian soldiers who had signalled their intention to surrender.
A short video posted on Telegram shows two men coming out of a shelter, one with his hands above his head, before lying on the ground in front of another group of soldiers.
This is followed by what appears to be gunfire, and smoke appears, before the video cuts off abruptly.
These undated images were aired on social networks as having been filmed near Avdiivka, a town in eastern Ukraine where fighting is raging.
But neither their location nor their authenticity could be confirmed by AFP.
Ukraine’s human rights ombudsman Dmytro Lubinets denounced the events as a “war crime”.
“Today, a video of the execution by Russian servicemen of Ukrainian soldiers who surrendered as prisoners appeared online! This is another violation of the Geneva Conventions and disrespect for international humanitarian law!” he wrote on Telegram.
“The Russian side shows its terrorist face again and again!” he added.
Lubinets said the Ukrainian soldiers “were disarmed, and their hands were raised… They did not pose any threat! The Russian side had to capture them and give them the status of prisoners of war.”
In March, another video went viral, appearing to show a Ukrainian soldier being shot dead after shouting “glory to Ukraine”.
At that time the UN High Commissioner for Human Rights, Volker Turk, said his office had documented numerous violations of international humanitarian law against prisoners of war.
These included “numerous summary executions and targeted attacks on civilians” by Russian forces and affiliated armed groups like the Wagner mercenary force, as well as “621 cases of enforced disappearances and arbitrary detention”.