“A terrorist attack was staged on one of the checkpoints inside the city of Manbij at midnight and as a result seven fighters on guard duty were martyred,” the Manbij Military Council said in a statement.
The UK-based Syrian Observatory for Human Rights described it as a “bloody attack” staged by a suspected Islamic State (ISIS) sleeper cell.
Later on Tuesday, ISIS claimed responsibility for the attack, AFP reported.
The target was a checkpoint of the self-defence forces on the Manbij-Aleppo road, the Observatory stated.
A number of other fighters were also injured, some critically, so the death toll may rise.
Manbij is in a state of alert while forces look for the perpetrators of the attack, according to the Observatory, noting the attack came a few days after the arrests of more than 100 people suspected of belonging to ISIS or associated with Turkish-backed forces.
The Syrian Democratic Forces (SDF) declared the end of the so-called ISIS caliphate in a ceremony in eastern Deir ez-Zor province on March 23.
At the ceremony, co-chair of the Syrian Democratic Council (SDC), Ilham Ahmed, said the next stage of the fight against ISIS is to eliminate sleeper cells and then combat the group’s ideology.
Manbij, located at a crossroads in northern Syria, was once an ISIS hub. It was liberated from the group in August 2016 by the SDF, led by the local Manbij Military Council and backed by the global coalition against ISIS.
The multi-ethnic city has remained a flashpoint, however, with Turkey repeatedly threatening a military operation to remove Kurdish forces from the city. The United States reached a deal with Turkey that has seen their two militaries conduct joint patrols in the Manbij area.
Four Americans, five Manbij forces, and nine civilians were killed in a suicide attack in the city in January.
Eight people – mainly civilians – were injured in a suicide bombing earlier this month.
