The head of Ukraine’s presidential office vowed for accountability late on Tuesday following publication of a video where a Russian military officer allegedly beheads a living Ukrainian soldier.

"There will be an answer and responsibility for everything," Andrii Yermak posted on Telegram.

The video, which LIGA.net has seen but does not publish here for ethical reasons, shows people in military uniforms with white ribbons – usually used for identification by the Russian military in Ukraine – beheading a living person in a uniform with Ukrainian insignia.

The faces of the people in the minute and a half video are covered by masks. One of the men, presumably a Russian soldier, is on a walkie-talkie and gives instructions to the other, who commits the murder with a knife.

The recording also shows the two men showing a bulletproof vest with Ukrainian insignia to the camera. A yellow ribbon – used by the Ukrainian military during the war – is visible on the uniform of the person being executed.

It is not known where the video was first published. Since bright green leaves are seen in it, it is possible that it could have been recorded earlier. LIGA.net cannot confirm the authenticity of the video.

If confirmed, it will be not the first time that the Russian military has executed Ukrainian soldiers.

In early March, an unarmed Ukrainian prisoner of war who said 'Glory to Ukraine!' was shot, with the video posted on social media.

Oleksandr Matsiievskyi, who was recognised as the executed Ukrainian solider, was awarded the title of Hero of Ukraine.