KYIV — Ukraine promised Wednesday to investigate a gruesome video circulating on social media that purportedly shows the beheading of a Ukrainian soldier.

The video spread quickly online and sparked outrage from Ukrainian officials. The Kremlin called the footage “horrible” but said it needed to be verified.

While the authenticity of the video or the circumstances of where and when it was shot have yet to be verified, the video appears to show a man in green fatigues wearing a yellow armband, typically donned by Ukrainian fighters. He is heard screeching before another man in camouflage uses a knife to decapitate him.

A third man holds up a flak jacket apparently belonging to the man being beheaded. All three men speak in Russian.

Since Russian forces invaded Ukraine more than a year ago, they have committed widespread abuses and alleged war crimes, according to the United Nations and human rights groups.

The International Criminal Court has also issued an arrest warrant for Russian President Vladimir Putin for war crimes. The Kremlin denies it has committed war crimes or that it has targeted civilians.

Ukrainian troops have also been accused of abuses, and last year Kyiv said it would investigate video footage circulated online that Moscow alleged showed Ukrainian forces killing Russian troops who may have been trying to surrender.

Ukrainian President Volodymyr Zelensky said the violence in the latest video would not be forgotten — and that Russian forces would be held responsible for such acts.

“Everyone must react, every leader. Do not expect that it will be forgotten, that time will pass,” he said in a video posted to his official Telegram channel.

In it, he used strong language to describe Russian soldiers, including calling them “beasts.”

Ukraine’s Foreign Minister Dmytro Kuleba also decried the footage on Twitter:

Kremlin spokesman Dmitry Peskov said that it’s necessary to thoroughly check the “horrible” video and verify that it is real.

“In the world of fakes we live in, the authenticity of the footage must be checked,” he said in a conference call with reporters.

Ukraine’s state security service launched an investigation into the video, according to a statement from Vasyl Maliuk, the head of the agency, known as the SBU.

Posters in some pro-Kremlin Russian Telegram channels, while not confirming the authenticity of the video, did not dispute it. Some sought to justify it by saying that Russian troops have become hardened by combat.

Andrei Medvedev, a Russian state TV journalist and a member of the Moscow city legislature, speculated that the timing of the video’s release was “fairly opportune” for the Ukrainian army, saying it could help “fire up personnel ideologically” ahead of a planned major counteroffensive.

Mykhailo Podolyak, an advisor to Zelensky, also linked the video’s release to the expected offensive, but said it was meant to “demoralize the public mood or at least change the psychological perception of the war right now.”

Ukraine’s ombudsman on Wednesday said that he will request that the UN Human Rights Committee investigate the video.

Dmytro Lubinets wrote on Telegram that “a public execution of a captive is yet another indication of a breach of the Geneva Convention’s norms, international humanitarian law and a breach of the fundamental right to life.” — Euronews