Extremist forces targeted a U.S.-controlled base in Syria with three rocket attacks Sunday, but the ordnance failed to strike U.S. forces or equipment.

The U.S. has yet to verify who was responsible for the attack, which targeted a base known as Green Village in northeastern Syria, according to CENTCOM. There have been several attacks on U.S. forces in Syria in recent months, varying from drone-carried explosives to infantry assaults.

"Three 107mm rockets targeted the base. A fourth rocket along with rocket tubes was found at the launch point, approximately 5 kilometers away," CENTCOM wrote in a statement. "U.S. forces in northeast Syria are investigating the incident."

The attack comes weeks after the U.S. carried out air strikes against Iranian-backed militants in the region.

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"We will respond appropriately and proportionally to attacks on our servicemembers," Gen. Michael Kurilla, commander of U.S. CENTCOM said in late August. "No group will strike at our troops with impunity. We will take all necessary measures to defend our people."

The air strikes came after three U.S. service members were injured in a rocket attack against another base.

A similar incident saw drones carrying explosives fly into a U.S. base in southern Syria.

American and allied forces at the al-Tanf compound suffered no injuries or damage from the attack, however. Troops stationed at the base shot down one of the drones before it could enter the compound. Another one flew inside a building and detonated but caused no injuries.

The U.S. garrison at al-Tanf conducts frequent patrols alongside coalition forces against Islamic State militants.