Two activist groups say an airstrike believed to have been carried out by the U.S.-led coalition has targeted a town controlled by al-Qaida militants in northwestern Syria.

The Local Coordination Committees and the Britain-based Syrian Observatory for Human Rights said Tuesday that the strike hit the town of Harem in Syria's Idlib province overnight. There was no immediate word on casualties.

It also was not immediately clear what was targeted, but Harem is controlled by al-Qaida's Syrian branch, known as the Nusra Front. U.S. aircraft bombed Nusra militants near Harem last week.

If the latest strike is confirmed, it would mark the fourth time that American aircraft have targeted the al-Qaida affiliate in the U.S.-led coalition's broader aerial campaign against Islamic extremists in Syria and Iraq.