A military outpost in southern Syria was hit by a coordinated attack on Wednesday, but a U.S. official said no American troops stationed there were injured or killed.

The official said the attack appeared to include at least one drone strike and possibly groundfire. It was not yet clear who carried out the attack.

U.S. and coalition troops are based at the al-Tanf garrison to train local Syrian opposition forces on patrols to counter Islamic State militants.

The base is also located on a road serving as a vital link for Iranian-backed forces from Tehran to all the way to southern Lebanon and Israel.

The official said there was no information on whether local forces were injured or killed in the attack. The official spoke on condition of anonymity to discuss military operations.