Al-Qaeda-linked rebels in Syria beheaded a man in front of a crowd that included children, according to the Britain-based Syrian Observatory for Human Rights monitoring group.

In an amateur three-minute video posted online by the Observatory over the weekend, armed men dressed in black stand around a man, reportedly a Shiite pro-regime fighter, lying in the grass. One of the armed militants takes out a small knife, and cuts off the head of the captive as the assembled crowd cheers.

The rebel holds up the decapitated head, then places it on the victim’s back before it rolls off onto the grass.

The remainder of the footage shows the crowd laughing and taking pictures.

The Observatory reported that the footage is from the Syrian city Homs, and the rebels are from the al-Qaeda-linked Islamic State of Iraq and the Levant.

Moderate and Islamist opposition fighters have been battling ISIL since early January, after accusing the group of a spate of abuses against civilians and rebels.

ISIL is allegedly behind most of the attacks that have been taking place recently in Iraq. It is also playing a more active military role alongside other predominantly Sunni rebels in the fight to topple Syrian President Bashar Assad, and its members have carried out attacks against Syrians near the porous border inside Iraq.

Internal clashes within the ranks of the rebels clashes have killed more than 1,400 people since they began a month ago, and the fighting shows little sign of coming to an immediate close.

On Saturday, a twin suicide bombing killed 26 people, including a senior military commander of the Tawhid Brigade, a prominent rebel group opposed to the Islamic State.

The attack, widely blamed by both pro- and anti-al-Qaeda activists on the Islamic State, targeted the base of its rivals in the Tawhid Brigade and killed senior leader Adnan Bakkour, said Observatory director Rami Abdurrahman.

The Islamic State also killed another prominent commander, Abu Hussein al-Dik of Suqour al-Sham, on Saturday near the central city of Hama, the Observatory said. Abdurrahman said al-Dik was killed in an ambush outside of Hama, where he was traveling to try to help rebels encircled by Islamic State fighters.

Both the Tawhid Brigade and Suqour al-Sham are part of the Islamic Front, a powerful alliance of seven Islamist rebel factions that united in November. The Islamic Front has emerged as a heavyweight in northern Syria, and has been a driving force in the fight against the Islamic State.

Analyst Charles Lister of the Brookings Doha Center said the Islamic State “appears to be targeting particularly strategic locales and individuals in its continuing operations against perceived enemy rebels.”

Syria’s conflict, which began in March 2011 as a street uprising against Assad’s rule, has killed more than 136,000 people, according to the latest count by the Observatory, which tracks the missing and killed through a network of informants on the ground.

The war has also forcibly displaced one-third of Syria’s prewar population of 23 million.

AFP contributed to this report.