ISIS on Tuesday claimed an attack killing seven US-backed fighters in the northern Syrian city of Manbij, days after their “caliphate” was declared defeated.
“The caliphate’s soldiers attacked a checkpoint... west of Manbij city last night,” said a statement published on the group’s social media channels.
Manbij is a former ISIS stronghold that is now ruled by a military council affiliated with the Syrian Democratic Forces (SDF), the US-backed Kurdish-led alliance which declared victory over ISIS in its last redoubt in eastern Syria on Saturday.
At around midnight (2200 GMT) on Monday, gunmen opened fire at fighters manning a checkpoint at the entrance to the city, killing seven, the council said. There was no immediate claim of responsibility.
Council spokesman Sherfan Darwish said it could be a revenge attack by ISIS sleeper cells. “After the victory over ISIS, we have entered the phase of sleeper cells,” Darwish told AFP. “These sleeper cells are being activated and carrying out attacks but we will foil their operations.”
The Syrian Observatory for Human Rights, a Britain-based monitor of the war, said the attack was probably the work of ISIS, which would make it “the first attack of its kind” since its defeat last week.
Observatory head Rami Abdul Rahman said it was also the bloodiest attack in Manbij since January 16, when 19 people, including four US service personnel, were killed in a suicide bombing claimed by ISIS.
ISIS has vowed to carry out revenge attacks against the SDF for the six-month offensive, which culminated in the group’s defeat in the village of Baghouz, close to the Iraqi border, on Saturday.
The Observatory said hundreds of SDF members had been killed in attacks believed to have been carried out by ISIS sleeper cells since August.
Manbij is also a major point of contention between the Kurds, who lead the SDF, and neighboring Turkey, which is deeply opposed to their autonomous administration in northeastern and parts of northern Syria.