Four rockets hit an Iraqi base hosting US-led coalition and Nato troops on Friday, causing material damage but no casualties, the Iraqi military said in a statement.
The Reuters news agency reported that the rockets hit the Besmaya base south of Baghdad, where Spanish troops have been based as part of the fight against the Islamic State (IS) group.
So far, no group has claimed responsibility for the attack.
In recent months, there have been several attacks against the US embassy in Baghdad or bases where foreign troops are deployed, killing a total of three American military personnel, one British soldier and one Iraqi soldier.
Washington has mostly blamed Kataeb Hezbollah, an armed militia backed by Iran and designated as a terrorist organisation by the US, for the attacks.
The White House has long insisted that the Baghdad government do more to rein in such factions, which make up part of the state-backed Hashd al-Shaabi paramilitary body.
Iraq's recently appointed Prime Minister Mustafa Kadhimi has vowed to prevent them from targeting American troops and diplomats, and late last month ordered a raid on the headquarters of Kataeb Hezbollah, resulting in 13 arrests.
Still, Friday's attack comes just days after three rockets landed near the US embassy in the Green Zone, which houses some of the Iraqi government's main offices and some foreign embassies.
Currently, there are about 5,200 American troops in the country, whose main missions are counterterrorism and training Iraqi forces. Pentagon officials have said they can do the job with about half that number, according to the New York Times.
Tensions simmered between Washington and Baghdad in January, when a US drone strike near Baghdad airport killed top Iranian general Qassem Soleimani and Iraqi militia commander Abu Mahdi al-Muhandis, prompting Iraqi lawmakers to vote in favour of ousting all foreign troops.
The situation has calmed since Kadhimi, an ex-spy chief with close ties to the US and its allies in the region, came to power in May.