The US treated 11 of its troops for symptoms of concussion after an Iranian missile attack on an Iraqi base where US forces were stationed, the US military said on Thursday, after initially saying no service members were hurt.

The attack was retaliation for a US drone strike in Baghdad on 3 January that killed Qassem Suleimani, the commander of the elite Quds force of Iran’s Revolutionary Guards.

Donald Trump and the US military had said there were no casualties after the strike on the al-Asad air base in western Iraq and a facility in its northern Kurdish region.

In his speech on 8 January responding to the strike, Trump said: “The American people should be extremely grateful and happy no Americans were harmed in last night’s attack by the Iranian regime. We suffered no casualties, all of our soldiers are safe, and only minimal damage was sustained at our military bases.”

Capt Bill Urban, a spokesman for US central command, said in a statement on Thursday: “While no US service members were killed in the 8 January Iranian attack on al-Asad airbase, several were treated for concussion symptoms from the blast and are still being assessed.”

As a measure of caution, some service members were taken to US facilities in Germany or Kuwait for “follow-on screening”, he added.

“When deemed fit for duty, the service members are expected to return to Iraq,” he said.

As many as 1,500 Americans were deployed at the vast base deep in Iraq’s Anbar desert.