Gunmen attacked a checkpoint of a U.S.-backed force in Syria early Tuesday in the northern town on Manbij, killing seven fighters, an official with the Kurdish-led group said. A war monitor blamed sleeper cells of the Islamic State group.
Sharfan Darwish of the Manbij Military Council told The Associated Press that it was unclear who was behind the attack, which came shortly
after midnight at one of the entrances to Manbij. He said the "martyrs were carrying out their mission of protecting Manbij."
The Britain-based Syrian Observatory for Human Rights, a war monitor, said members of an IS sleeper cell carried out the attack, and that three other Manbij Military Council fighters were also wounded.