Blast kills US soldiers in Iraq

US forces are frequently targeted in the "Sunni Triangle"

A powerful explosion has killed three US soldiers and wounded a fourth west of the Iraqi capital Baghdad, a US military source reports.

A roadside bomb appears to have gone off in the town of Khaldiya, an official at Central Command told Western news agencies.

The area has seen regular attacks by militants opposed to the occupation.

Witnesses said two bombs had exploded - one as a US convoy passed and the second when reinforcements arrived.

Hospital staff said two Iraqis were also killed - one of them shot in the stomach as he stood in his office nearby.