No U.S. troops were injured Friday morning when about 25 Islamic militants dressed in Iraqi army uniforms attacked the perimeter of al-Asad Air Base in Anbar province, Iraq, a defense official said.

The 300-plus U.S. troops deployed to al-Asad who are conducting an advise-and-assist mission with Iraqi forces were "several miles away" at a far end of the sprawling desert installation, the official said.

"At no time were U.S. troops anywhere near the fighting," Rear Adm. John Kirby, a Pentagon spokesman, told reporters Friday. "They might have heard shots being fired, but that would have been about it."

American troops provided some intelligence from surveillance assets to help the Iraqi forces. Yet the Iraqis suppressed the attack without U.S. airstrikes, which have become common in the area around al-Asad.

"Iraqi forces were there at the scene, engaged them immediately and the attack failed," Kirby said.

"The Iraqi security forces did this on their own," Kirby said, adding that the incident "proves that the Iraqi forces can fight effectively."

Al-Asad has faced ineffective mortar fire in recent months, but the unusually brazen Friday morning attack appeared to be the most aggressive since U.S. troops arrived there last year.

It came after Islamic State forces this week seized control of the western Iraqi town of al-Baghdadi, just a few miles from heavily guarded al-Asad.

Kirby said the fall of al-Baghdadi does not signal that the Islamic State group is gaining momentum.

"This is still an enemy that we assess to be in a defensive posture," Kirby said.

That said, the Sunni Islamic militants now control most of Anbar province and its border with Syria.

The U.S. troops at al-Asad are training about 800 Iraqi forces, according to the statement.

Total U.S. troop strength in Iraq stands at about 2,600.

Islamic State forces routinely operate close to al-Asad. According to the Defense Department, recent U.S. and coalition airstrikes near the base:

Feb. 11: Struck an IS mortar position.

Feb. 8: Denied the IS terrain.

Feb. 5: Struck an IS tactical unit and an IS staging location.

Feb. 4: Struck an IS staging location.

Feb. 3: Struck an IS tactical unit.

Feb. 1: Struck an IS tactical unit and destroyed a mortar position and a fighting position.

Jan. 31: Struck an IS tactical unit.

Jan. 30: Destroyed an IS rocket tube.