An appalling video emerged Tuesday showing what appears to be a Russian soldier savagely beheading a Ukrainian prisoner of war with a knife, leading Kyiv to compare Vladimir Putin’s regime to ISIS.

The footage, which has been circulating on pro-Russian Telegram channels, shows an apparent Russian serviceman slicing into the neck of a captive wearing a yellow armband associated with Ukrainian forces.

The unidentified victim is still alive at the start of the decapitation and is heard begging: “It hurts, stop.”

The executioner’s comrades cheer him on in the background, urging him to “f—ing cut it, break the spine! What, have you never cut off heads before?”

Another person speaking in Russian off-camera suggests placing the POW’s severed head in a bag and “sending it to the commander.”

The Post could not independently verify the authenticity of the video.

It has been suggested that the sickening footage was likely filmed last summer, judging by the amount of plants visible on the ground at the site of the killing.

The video has sent shockwaves through Ukraine, with President Volodymyr Zelensky demanding that the killers be brought to account.  

“There is something that no one in the world can ignore: how easily these beasts kill,” Zelensky said in a video message Wednesday. “We are not going to forget anything. Neither are we going to forgive the murderers. There will be legal responsibility for everything. The defeat of terror is necessary.”

Ukrainian Foreign Minister Dmitro Kuleba wrote on Twitter: “It’s absurd that Russia, which is worse than ISIS, is presiding over the UNSC,” referring to the UN Security Council, where Russia took up the rotating presidency this month.

“Russian terrorists must be kicked out of Ukraine and the UN and be held accountable for their crimes,” Kuleba added.

Kremlin spokesperson Dmitry Peskov told reporters at a daily briefing that the footage was “terrible,” but he also sounded a skeptical note, saying: “First of all, in the world of fakes that we live in, we need to check the veracity of this footage.”

He continued: “Then it could be a pretext to check whether or not this is true, whether it happened, and if it did, where and by whom.”

Ukraine’s foreign ministry called on the International Criminal Court to “immediately investigate yet another atrocity of the Russian military.”

Ukraine’s domestic security agency, SBU, said it had opened its own investigation into a suspected war crime over the video.

“Yesterday, a video appeared on the Internet showing how the Russian occupiers are showing their beastly nature – cruelly torturing a Ukrainian prisoner and cutting off his head,” the SBU agency wrote on Telegram.

The release of the execution video came just days after another recording emerged online, showing purported members of Russia’s notorious Wagner mercenary group displaying the beheaded and mutilated bodies of two Ukrainian soldiers lying on the ground next to a mangled armored vehicle.

A digitally distorted voice is heard saying in Russian with a laugh: “They killed them. Someone came up to them. They came up to them and cut their heads off.”

According to information shared on Russian Telegram accounts, that video was shot near Bakhmut in eastern Ukraine — a key town that Russian forces led by the Wagner Group have been fighting to capture for months.  

Yevgeny Prigozhin, the founder of the Wagner Group, said he had watched the video, but he attempted to distance his fighters from the atrocity.

“It’s bad when people get their heads cut off, but I didn’t find anywhere that this is happening near Bakhmut or that Wagner fighters are taking part in the execution,” he said in a statement to The Daily Beast.

In Geneva, the UN Human Rights Monitoring Mission in Ukraine said it was appalled by what it called “particularly gruesome” videos posted on social media.

“Regrettably, this is not an isolated incident,” it said in a statement. “The latest incidents must also be properly investigated and the perpetrators must be held accountable.”