In the latest atrocity of the Syrian civil war, Reuters reports that Al-Qaeda-linked rebels have executed the commander of a rival rebel faction and six of his men.

An amateur video of the public execution was posted online, the news agency reported.

The Islamic State in Iraq and the Levant (ISIL), a jihadist group fighting to overthrow President Bashar Al-Assad, has taken advantage of a power vacuum in rebel-held areas to assert its authority over more moderate elements of the armed opposition.

The video, posted online by the anti-Assad Syrian Observatory for Human Rights monitoring group on Wednesday, shows armed men in black standing below an ISIL banner.

The Observatory said the video was taken in the northern Syrian town of Atarib in Idlib province. Its authenticity could not be independently confirmed.

A masked man on the video identifies seven men kneeling as members of the Ghurabaa al-Sham brigade, a moderate Islamist group that was one of the first to fight Assad. A man who appeared to be the group’s commander, Hassan Jazera, was among them.

“Hassan Jazera is the most corrupt and the biggest thief,” said the man. He spoke into a microphone to a crowd of men, some of whom used their mobile phones to film the killing.

The man, reading from a piece of paper, said Jazera’s men were also charged with kidnapping and had been tried in a religious court run by ISIL. They were then shot in the head.

Jazera and his men were arrested by ISIL a month ago, the UK-based Observatory said, according to Reuters.

The rebels have long ago split into rival factions and have begun fighting one another, essentially creating a second civil war in Syria.

In Aleppo, several Islamist groups split off from the Western-backed Syrian National Council declared the region to be an independent Islamist state.

The jihadists in Aleppo have set up a court based on Sharia (Islamic law) which is authorized to issue execution orders for serious offenses.

These executions, usually carried out by beheading those convicted, are a regular occurrence and an example of atrocities carried out by the rebels.

Several weeks ago, jihadist rebels had to ask for "understanding and forgiveness" after they beheaded the wrong man.

The rebels published a video showing the head of a man they said was part of a Shiite militia fighting for Assad. As it turned out the head belonged to a member of another jihadist rebel group.

Several months ago, a Catholic priest who was accused of collaborating with Assad’s regime was publicly beheaded, with the execution filmed and posted to the Internet for all to see.

Some of the Islamist groups have attempted to soften their image in an attempt to win hearts and minds - holding stand up comedy shows and handing out toys to local children.

A British think-tank said this week that more than 11,000 children have died in Syria's civil war, including 128 killed by chemical weapons.

In addition to clashes between rebels, there have also been numerous clashes between Arab rebel groups and Kurdish militias in the northern part of Syria - essentially a third civil war.