A roadside bomb killed two US soldiers and one Iraqi in the city of Khalidiyah today.
A military spokesman said at least one Iraqi was also killed and another US soldier injured in the attack. He was not certain if the Iraqi was a civilian.
Last night, militants launched dozens of mortars and rockets at the main US prison in Baghdad and troops killed one Iraqi as they returned fire last night, the US military said.
The attackers fired 33 mortar rounds and five rockets at the Abu Ghraib prison, where US forces hold hundreds of Iraqi detainees, a US military official said. "Coalition forces engaged and killed one enemy as he tried to flee the scene."
US soldiers arrested 55 others at the scene.
The prison on Baghdad's outskirts in Abu Ghraib, where toppled Iraqi president Saddam Hussein once kept his enemies, has been renamed the Baghdad Correctional Facility by the US occupation.
Hundreds of prisoners are held there for suspected involvement in attacks against the US-led occupation forces or for ordinary crimes.