A group of Syrian Sunni Muslim rebels linked to Al-Qaida have beheaded one of their own wounded fighters after mistaking him for a foreign Shi’ite fighting for President Bashar Assad, a monitoring group said yesterday.

A video posted by the Syrian Observatory for Human Rights shows two members of the Islamic State of Iraq and the Levant (ISIL) brandishing a severed head before a crowd in Aleppo and saying he was an Iraqi Shi’ite fighting for Assad.

Observatory head Rami Abdelrahman said that the man was later identified by the Ahrar al-Sham group, which fights alongside ISIL, as Mohammed Marroush, one of its fighters.

“(ISIL) admitted that they killed the rebel, and arrested a Tunisian man for cutting his head off,” Abdelrahman said, adding that the Tunisian had been referred to an Islamic rebel court in Aleppo.

Marroush had been wounded in fighting around Aleppo and taken to a hospital for treatment, where ISIL fighters said they had heard him repeat the name of two venerated Shi’ite imams, Ali and Hussein, Abdelrahman said.

Activists in Aleppo said that Marroush, who was anaesthetised, might have thought he had been captured by pro-Assad militiamen and so pretended to be a Shi’ite.

Many Shi’ites have come to Syria from Iraq or Lebanon to help Assad, whose ruling establishment are mostly members of a sect linked to Shi’ite Islam, fight a majority Sunni revolt.

But the myriad rebel groups are not only fighting Assad but also competing with each other to secure territory or power.

Ahrar al-Sham issued a “wanted poster” on its website for the two men seen in the video with the severed head. ISIL did not respond to requests for comment.

Both sides in the conflict have been accused by rights groups of war crimes, and residents say they face oppression at the hands of Assad’s forces and loyalist militias on one hand and hardline Islamist rebels on the other.