Rocket and drone attacks on Wednesday targeted bases in Iraq and Syria hosting US forces that are part of an international coalition fighting the Islamic State jihadist group.

Fourteen rockets were fired at an air base hosting American troops in Iraq's western province of Anbar, causing minor injuries to two personnel, the US-led coalition said.

It was the latest in a spate of attacks on US military and diplomatic facilities in Iraq, blamed on pro-Iranian armed groups within a state-sponsored paramilitary force.

US forces, who have 2,500 troops deployed in Iraq as part of the anti-IS coalition, have been targeted almost 50 times this year in the country.

A Shite militant group called Revenge of al-Muhandis Brigade claimed responsibility and vowed to defeat the "brutal occupation", according to the US-based SITE intelligence group which monitors extremist groups.

The militant group is named after Abu Mahdi al-Muhandis of Iraq's Hashed al-Shaabi paramilitary alliance, who was killed in a US drone strike early last year along with the revered Iranian general Qasem Soleimani, SITE said.

Late last month, the US carried out deadly air strikes against pro-Iran fighters in both Iraq and Syria.

On Wednesday, the Ain al-Assad base was attacked by 14 rockets that "landed on the base & perimeter," coalition spokesman Wayne Marotto wrote on Twitter.

Iraqi security forces said the rocket launcher had been hidden inside a truck carrying bags of flour.

US forces on Monday night shot down an armed drone above their embassy in Baghdad, according to Iraqi security officials.