Syrian jihadist group accidentally beheads a rebel from another jihadist group, then asks for "understanding and forgiveness".

Jihadist rebels in Syria had to ask for "understanding and forgiveness" after they beheaded the wrong man, the British Telegraph reports.

In a public appearance filmed and posted online, members of the Al-Qaeda-affiliated Islamic State of Iraq and al-Sham (ISIS), one brandishing a knife, held up a bearded head before a crowd in Aleppo.

The jihadists triumphantly described the execution of what they said was a member of an Iraqi Shiite militia fighting for President Bashar Al-Assad.

As it turned out, reported the Telegraph, the head belonged to a member of Ahrar al-Sham, which is a Sunni jihadist rebel group that often fights alongside ISIS, though it does not share its Al-Qaeda ideology.

After inquiries, an ISIS spokesman admitted the beheaded man was Mohammed Fares, an Ahrar commander reported missing some days ago.

The Syrian Observatory of Human Rights, an organization which monitors deaths in the Syrian conflict, said that ISIS rebels misunderstood comments Fares had made, resulting in his beheading.

Other reports indicate that in the fog of battle, Fares - who was wounded in fighting around Aleppo - thought he had been captured by a Shiite militia, and offered up Shiite prayers in an attempt to hide his Sunni identity. Sunni Islamist fighters overheard his prayers, assumed he was a Shiite, and beheaded him.

The incident underlines not only the cruelty of the jihadist rebels, but also the deep divisions between the jihadist rebels and the Western-backed more moderate rebels.

Nearly a year ago, several Islamist groups split off from the Western-backed Syrian National Council opposition force and declared Aleppo 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.

Beheading those who are deemed to be “collaborating” with the Assad regime is a regular occurrence and an example of atrocities carried out by the rebels. 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 second civil war has begun in war-ravaged Syria as the more moderate rebel groups and the Islamist extremist groups are also fighting each other, in addition to fighting Assad’s troops. There have also been numerous clashes between Arab rebel groups and Kurdish militias in the north of the country.