The UN's peace envoy to Syria has warned there is 'no end in sight' to the civil war (AP)

A Syrian woman stands amid the ruins of her house which was destroyed in an airstrike by government warplanes a few days earlier, killing 11 (AP)

Flames and smoke rising from burned cars after a huge explosion that shook central Damascus (AP/SANA)

A Syrian villager, Abu Ibrahim, 73, writes the name of his granddaughter on her grave after she was killed in an airstrike by the government (AP)

A woman walks through the mud in a refugee camp in Syria (AP)

Muddy boots belonging to Syrian refugees are seen at the entrance of a tent in a refugee camp near Azaz, north of Aleppo province, Syria (AP)

A Syrian woman sits on the ruins of her house following an air strike in Aleppo (AP)

An Assad supporter holds up a picture of the president (AP)

A video image shows an explosion during heavy fighting between rebels and Syrian government forces in the Barzeh district of Damascus (AP)

This photo released by the Syrian official news agency SANA, shows Syrians inspecting a damaged car at the scene of a car bomb exploded in the capital's western neighborhood of Mazzeh, in Damascus, Syria, Monday, April. 29, 2013

This photo released by the Syrian official news agency SANA, shows Syrians inspecting a damaged car at the scene of a car bomb exploded in the capital's western neighborhood of Mazzeh, in Damascus, Syria, Monday, April. 29, 2013

Rebels and troops loyal to Syrian President Bashar Assad have fought at two air bases in northern Syria (AP)

Free Syrian Army fighter puts up a FSA flag after heavy clashes at a military academy besieged by the rebels in Tal Sheer (AP)

The damage caused by an explosion at the Syrian interior ministry in Damascus (AP)

Trucks pass a mountain of garbage in Aleppo, where there has been heavy fighting and shelling between the Syrian Government and rebels (AP)

Rebel fighters in Syria run for cover through smoke from an explosion (AP)

A Free Syrian Army fighter aims his weapon at government forces during clashes in Aleppo (AP)

This citizen journalism image shows members of the free Syrian Army hiding behind scrap metal during an attack against Syrian government forces (AP Photo)

A Free Syrian Army fighter holds his weapon as he prepares himself for advance, close to a military base, near Azaz (AP)

Syrian soldiers prepare an anti-aircraft gun near field of wheat close to a radar position in eastern Lebanon's Bekaa valley (AP)

A Syrian rebel commander has been filmed cutting open a dead man’s chest, ripping out his heart and biting into it.

A blurred and cut version of the video was widely circulated online, but New York-based Human Rights Watch said a longer clip in its possession contained sectarian slurs against Alawites, the sect to which President Bashar al-Assad belongs.

Khalid al Hamad (who goes by the nom de guerre Abu Sakkar), 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.”

The act of mutilation is a brutal example of the sectarian revenge killings becoming 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.

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 Army has been making a number of strategic gains in recent weeks, particularly around the strategic town of Al Qusayr, close to the Lebanese border.

Israeli Prime Minister Benjamin Netanyahu has landed in Russia for talks with Russian President Vladimir Putin, where he is expected to press him not to supply advanced anti-aircraft systems to Syria.

Belfast Telegraph