A roadside bomb killed four U.S. soldiers in Baghdad on Sunday, the military said, bringing the number of U.S. military deaths to 4,000 since the invasion of Iraq in 2003.

The statement by U.S.-led coalition forces on Monday said one U.S. soldier was wounded in the attack.

The U.S. soldiers were killed at around 10 p.m. local time while on patrol in vehicles in southern Baghdad, it said.