"Two US soldiers were killed and one wounded at 10:30 this morning (07:30 GMT) in a roadside blast near Khalidiya," a military spokesman in Iraq said on Thursday.
"One Iraqi translator and one Iraqi policeman workiing with the coalition foces were also killed in the attack."
Thursday's deaths brought to 378 the number of US soldiers killed in hostile action in Iraq since the war erupted in March.
Khalidiya is around 60 km west of Baghdad, in a volatile region of strong resistance to the US-led occupation of Iraq.
The attack came after resistance fighters launched dozens of mortars and rockets at the main US prison in Baghdad on Wednesday evening and troops killed one Iraqi as they returned fire.
The attackers fired 33 mortar rounds and five rockets at the Abu Ghraib prison, where US forces hold hundreds of Iraqi detainees, at about 06:30pm (15:30 GMT), a US military official said on Thursday.
"Coalition forces engaged and killed one enemy as he tried to flee the scene."
One anti-occupation fighter was
killed in Abu Ghraib prison attack
US soldiers arrested 55 others at the scene.
One US soldier suffered minor wounds, but was treated and returned to duty.
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 forces or for ordinary crimes.