Iraqi officials say a mortar attack on a joint U.S.-Iraqi military base south of Baghdad has killed five civilians.

The officials say insurgents fired several mortars Monday at the base in the mainly Shi'ite city of Diwaniyah. Police say five civilians outside the base were killed in the attack, including two children. About 20 people were wounded.

There was no immediate word on military casualties or damage at the base.

In another development, a U.S. military court near Baghdad began a court-martial today for an American officer charged with aiding the enemy and other offenses.

The defendant, Lieutenant Colonel William Steele, is the former head of a U.S. detention center in the Iraqi capital that held dictator Saddam Hussein before his execution.

Prosecutors accuse Steele of providing an unmonitored mobile phone and other special privileges to detainees, acting inappropriately with an interpreter and failing to obey an order. He faces life imprisonment if convicted.

Steele pleaded guilty to three of the seven charges against him at a pre-trial hearing earlier this month.

Some information for this report was provided by AFP, AP and Reuters.