Two drones attacked the Ayn al-Asad Airbase in Iraq's western Anbar province on Tuesday, where U.S. troops are stationed, an Iraqi army officer said.

The drones caused no casualties as they hit the airbase perimeter, the officer told Xinhua on condition of anonymity.

U.S. helicopters were seen flying over the airbase and surrounding areas, and Iraqi forces raised their alert level, according to the officer.

The Islamic Resistance in Iraq has carried out more than 175 rocket and drone attacks against US-led troops in Iraq and Syria in recent months.