Video has surfaced showing what appear to be Ukrainian soldiers shooting men who are apparently Russian prisoners in the knees during an operation in the Kharkiv region.
On the almost six-minute-long video, the Ukrainian soldiers are heard saying they have captured a Russian reconnaissance group operating from Olkhovka, a settlement in Kharkiv roughly 20 miles from the Russian border.
Asked about the video, a senior presidential advisor, Oleksiy Arestovych, said in an interview posted on YouTube Sunday: "The government is taking this very seriously, and there will be an immediate investigation. We are a European army, and we do not mock our prisoners. If this turns out to be real, this is absolutely unacceptable behavior."
In a separate briefing, Arestovych said, "We treat prisoners in accordance with the Geneva Convention, whatever your personal emotional motives."
CNN has reached out to the Ukrainian Defense Ministry for comment. In response, the ministry sent CNN a statement from the Armed Forces chief, Valerii Zaluzhnyi. The statement did not refer directly to the incident, but said, "In order to discredit Ukraine's defense forces, the enemy films and distributes staged videos showing inhuman treatment by alleged 'Ukrainian soldiers' of 'Russian prisoners.'
"I emphasize that servicemen of the Armed Forces of Ukraine and other legitimate military formations strictly adhere to the norms of international humanitarian law," Zaluzhnyi said. "I urge you to take into account the realities of informational and psychological warfare and trust only official sources."
It's unclear which Ukrainian unit may have been involved. The soldiers speak in a mixture of Ukrainian and Russian with Ukrainian accents.
The video comes as Ukrainian forces make gains east and south of Kharkiv. CNN geolocated and verified a long video uploaded on a Telegram Saturday showing a successful assault by Ukrainian troops of the Azov Battalion, in which they took a number of Russian prisoners in a rapid assault on Olkhovka, also known as Vilkhivka.
Some of the prisoners were stripped and blindfolded.
That video was posted by Konstantin Nemichev, a Kharkiv regional official who took part in the attack on Olkhovka. He told CNN he was not associated with the footage that emerged showing Ukrainian troops kneecapping Russian prisoners.
“This is not our location … I have not seen such a location,” he told CNN on Sunday.
He suggested the video was shot “maybe somewhere in the [Kharkiv] region.”
In the first response from Russian authorities, the chairman of the investigative committee of the Russian Federation, A.I. Bastrykin, said an investigation would be launched "to establish all the circumstances of the ill-treatment of captured soldiers by Ukrainian nationalists."
In a statement, Bastrykin said: "Footage appeared on the Internet in which prisoners were treated with extreme cruelty by Ukrainian nationalists. The video circulating online shows captured soldiers, being shot in both legs and not given medical assistance. According to some reports, illegal actions took place at one of the bases of the Ukrainian nationalists in Kharkiv region."
CNN is not showing the video.