A group of soldiers can be seen in the video pinning a member of Ukraine’s armed forces to the ground, before using a knife to strip his clothes and mutilate him. It is unclear what happened to the Ukrainian soldier, but it is unlikely that he would have survived his injuries without immediate medical attention. The footage, which was initially shared on pro-Russian channels on the Telegram messaging app, has since been circulated on Twitter and pro-Ukrainian Telegram channels. An adviser to the Ukrainian president on Friday confirmed the authenticity of the video and vowed to bring the perpetrator to justice. “The world must realize: Russia is a country of cannibals who enjoy torture and murder,” tweeted Mikhail Podoliak. “But the fog of war will not help to avoid punishment for the executioners. We will recognize and contact each of you.” Ukrainian MP Inna Sovsun added: “Russia must pay for this. Give Ukraine the weapons we need to stop this nightmare once and for all. People can’t pretend this isn’t happening.” It is unclear when and where exactly the video was recorded, but some of the Russian soldiers filmed in the video have appeared in separate propaganda videos broadcast by Kremlin-controlled news agencies. Since the gruesome video was shared online, internet sleuths have been scrambling to identify the soldier responsible, who was wearing a distinctive hat. Aric Toler of investigative website Bellingcat tweeted that the unit had been traced to Russian media reports from the seized Azov chemical plant in Severodonetsk, which was seized by Moscow forces in June. The group of Russian soldiers are believed to be from Akhmat Grozny’s special forces unit from Russia’s Chechnya region. This unit has previously filmed itself taking part in multiple operations as part of the Russian invasion of Ukraine. But the trousers worn by the attacker could also indicate the involvement of troops from the Rosgvardia unit – the Russian national guard reporting directly to Vladimir Putin. An adviser to Ukraine’s interior minister posted extensive personal and contact information on the suspected Russian soldier on social media on Friday, but has since deleted the post. In Russian-held Donetsk, separatist authorities on Friday accused Ukraine of shelling a prison colony where Ukrainian prisoners of war were being held in an attack that has since been hotly contested. At least 53 prisoners were killed and 75 others wounded, Donetsk separatist defense forces claimed. Footage released by Russian state television on Friday appeared to show a prison apartment with charred bunk beds and other items strewn around. Body parts and shoes were seen scattered on the floor. The separatists claimed that Ukrainian forces targeted the prison to punish troops who allegedly surrendered and were to testify against Ukraine. “Kiev’s criminal regime deliberately destroys surrendered Ukrainian fighters to cover up traces of war crimes against Donbas civilians and force others to continue fighting and not surrender,” it said. Ukraine’s General Staff disputed the attack and said on Friday that Russian artillery hit the prison in Olenivka. “The Russian occupiers pursued their criminal goals: to accuse Ukraine of committing war crimes and to cover up torture and executions of prisoners and executions,” the Ukrainian military said in a statement.