The U.S. conducted a counterterrorism operation in northern Syria, according to a statement the released by the Pentagon early Thursday.

“U.S. Special Operations forces under the control of U.S. Central Command conducted a counterterrorism mission this evening in northwest Syria,” the statement read. “The mission was successful. There were no U.S. casualties.”

The Pentagon did not say who the attack targeted. Northwest Syria is controlled by Turkey-aligned fighters and houses many jihadist organizations.

The Syria Civil Defence, the rescue organization known as the White Helmets, tells NPR that 13 civilians died in bombings and clashes, including six children. The group said it received initial word of an airborne raid shortly after midnight, and clashes and bombings continued after the initial air raid. They lasted until 3:07 AM, “when helicopters exited the scene.”

The attack targeted a two-story building in the town of Atmeh near the Turkey-Syria border.

The Associated Press reports this was the largest strike in Idlib since the 2019 strike that killed ISIS leader Abu Bakr al-Baghdadi, which also killed civilians. Residents in Atmeh told the AP they witnessed a large ground assault, and that American forces used loudspeakers warning women and children to flea.