The Pentagon says a small number of Islamic State fighters who attacked an Iraqi air base that hosts about 400 U.S. forces were killed in a counterattack by Iraqi troops.

Army Col. Steve Warren, a Pentagon spokesman, says initial reports Friday were that all eight IS attackers were killed by Iraqi troops at or inside a gate to al-Asad air base in the western province of Anbar. Warren said details were incomplete.

Warren said that no U.S. troops were involved in the fighting and says the Americans were about two miles away, in a different section of the sprawling air base.

Warren said that U.S. unmanned surveillance aircraft and Army Apache attack helicopters were sent to the scene but did not engage in fighting.