“Five mortar rounds were fired from the Jihad district (of southern Baghdad) at the American camp at around 9:30 pm (1830 GMT),” a police official said.
Jihad was once a stronghold of the Mahdi Army, the militia of radical anti-US Shiite cleric Moqtada al-Sadr.
US spokeswoman Major Janet Herrick confirmed the attack.
“Victory Base Complex received indirect fire Tuesday night at approximately 9:30 pm,” she said.
“Damages are currently being assessed. The incident is currently under investigation.