WASHINGTON (AFP) - At least 11 American troops were injured in an Iranian attack on an Iraqi base where American soldiers were deployed, United States Central Command said on Thursday (Jan 16), although the US military had previously maintained there were no casualties.

"While no US service members were killed in the Jan 8 Iranian attack on Ain al-Asad Air Base, several were treated for concussion symptoms from the blast and are still being assessed," US Central Command spokesman Captain Bill Urban said in a statement.

At the time of the attack, most of the 1,500 US soldiers at the base had been tucked away in bunkers, after advance warning from superiors.

The strike caused significant material damage but no casualties, according to previous reports from the US military.

US President Donald Trump also said on the morning following the volley that "no Americans were harmed in last night's attack".

However, Capt Urban said that "in the days following the attack, out of an abundance of caution, some service members were transported from al-Asad Air Base".

"At this time, eight individuals have been transported to Landstuhl, and three have been transported to Camp Arifjan," he said, referring to Landstuhl Regional Medical Centre in Germany and Camp Arifjan in Kuwait.

In addition to the sprawling Ain al-Asad air base in western Iraq, Iran's missiles also targeted a base in Arbil, housing both American and other foreign troops deployed in a US-led coalition fighting the remnants of the Islamic State group.

"When deemed fit for duty, the service members are expected to return to Iraq following screening," Capt Urban said.