A chilling video,  showing a Syrian rebel commander cutting open a dead man’s chest, ripping out his heart and biting into it drew widespread condemnation and is evidence that the country’s civil war has rapidly descended into sectarian violence and revenge killings, Human Right Watch (HRW) saidon Monday.

Khalid al Hamad, who goes by the pseudonym Abu Sakkar, and is a rebel commander with the Homs-based Farouk Brigades, claimed responsibility for the act in an interview with Time.

“Hopefully we will slaughter all of them [Alawites],” he said. “I have another video clip that I will send to them. In the clip I am sawing another Shabiha [pro-government militiaman] with a saw.”

According to HRW, the video shows Abu Sakkar cutting into the torso of a dead soldier. The footage has sparked outrage among both the opposition and supporters of Syrian President Bashar Assad.

While the man, who is allegedly Sakkar, is cutting open the soldier’s liver, the person filming says, “God Bless you, Abu Sakkar, you look like you are drawing [carving] a heart of love on him.”

After he cuts out the dead soldier’s liver and heart, he is filmed holding the organs in his hands and speaking into the camera: “I swear to God we will eat your hearts and your livers, you soldiers of Bashar the dog.” 

At the end of the video – the content of which cannot be independently verified – the man is filmed putting the soldier’s heart into his mouth, as if taking a bite out of it.

Human Rights Watch Emergencies Director Peter Bouckaert says that he had seen an original, unedited copy, of the video and that Sakkar’s identity had been confirmed by rebel sources in Homs. He said that Sakkar had been seen in other videos, wearing the same black jacket, which he is wearing in the last video clip, and the same rings on his fingers.

Bouchaert said that in the edited version of the film, Sakkar tells his men to “slaughter the Alawites and take their hearts out to eat them,” before biting into the heart.

“The mutilation of the bodies of enemies is a war crime, but the even more serious issue is the very rapid descent into sectarian rhetoric and violence,” Bouckaert said.

The act of mutilation is a brutal example of the sectarian revenge killings that have become increasingly common in the two-year conflict, and will further complicate Western efforts to provide more substantial backing to the disparate groups of the Free Syrian Army.

British Foreign Office Minister Alistair Burt condemned the “barbarous act” shown in the video, adding: “This is not Syria’s future.”

The Syrian National Coalition condemned the act as “horrific” and said it would investigate and bring the perpetrator to justice.

“One important way to stop Syria’s daily horrors, from beheadings to mutilations to executions, is to strip all sides from their sense of impunity,” said Nadim Houry, Middle East Deputy Director at Human Rights Watch. He called on members of the UN Security Council to support the referral of war crimes on both sides to the International Criminal Court.

The emergence of the video comes just a day after Prime Minister David Cameron announced he would double military support to the rebels.

The Syrian uprising against Assad is led by the majority Sunni Muslims. Assad, whose family has ruled for over 40 years, draws most of his support from his own Alawite sect, an offshoot of Shia Islam. 

The Syrian conflict, which began in March 2011, has resulted in the deaths of over 70,000 people, according to UN estimates.

 Aother video published May 9 showed fighters of the al Qaeda-linked Nusra Front in Syria executing 11 men they accused of taking part in massacres by President Assad’s forces.

The film is believed to be from eastern Deir al-Zor province and dates from some time in 2012, according to the Syrian Observatory for Human Rights, an opposition monitoring group.

The Observatory’s head, Rami Abdelrahman, said the Nusra Front has recently been releasing several videos of their past operations. He said the man seen executing the prisoners in the video – a Nusra commander – had been killed in March 2013 in battles with local tribes in the province.

The footage shows the commander, his face covered in a black balaclava, shooting each prisoner in the back of the head as they knelt, blindfolded and lined up in a row in the sand.

“The sharia court for the eastern region in Deir al-Zor has sentenced to death these apostate soldiers that committed massacres against our brothers and families in Syria,” the executioner said on the video.

The executioner returned to some victims, firing more bullets into them to make sure they were dead.

Videos of executions and torture have become increasingly common in Syria, where more than 94,000 people have been killed in a conflict now in its third year, according to the British-based Observatory, which has a network of activists in Syria.

Such videos posted online are hard to verify due to government restrictions on access for independent media.

A third video issued on May 14 from the northern province of Raqqa, which is controlled by Islamist rebels, showed three blindfolded men sitting on the curb of a central roundabout before being shot in the head with a pistol.

A man speaking in the video said the executions were revenge for killings in the coastal town of Banias two weeks ago. Photos and videos of the alleged Banias massacre showed dozens of mutilated bodies, many of them children, lying in the streets.

Meanwhile, U.N. General Assembly vote on May 14 on a draft resolution condemning Assad and his forces, indicated growing concern over extremism in Syria’s rebel movement.

While the non-binding text has no legal force, resolutions of the 193-nation assembly can carry significant moral and political weight. 

There were 107 votes in favor, 12 against and 59 abstentions – a drop in support compared with a resolution condemning the Syrian government that passed in August with 133 votes in favor, 12 against and 31 abstentions. U.N. diplomats cited concerns that Syria could be headed for “regime change” engineered by foreign governments and fears about a strengthening Islamist extremist element among the rebels as reasons for the decline in support for the resolution.

Segments of Syria’s fractured opposition carrying out such revenge killings may make U.N. member states reluctant to send arms. The U.N. resolution demands an immediate end to all violence and called violations of human rights widespread and systematic. 

The Syrian National Council accepted the draft but said more needed to be done. Russia voted vehemently against the resolution, saying it could hinder efforts to reach a diplomatic solution during a U.S.-Russia hosted peace conference.