In the new air strikes, F-16 fighter-bombers dropped three 500-pound bombs near the flashpoint town of Falluja, in the area west of Baghdad where 16 American soldiers were killed when a US Chinook helicopter was downed a week ago.

The air strikes early on Sunday followed attacks on US troops, a US military source said. He had no precise details.

Meanwhile, several loud explosions echoed across Baghdad on Sunday night and police said a mortar bomb hit a house in the city centre, but there were no immediate reports of casualties and little damage. It appeared to be the fourth mortar attack by insurgents in the past week on the capital.

Residents said no one was hurt when the mortar bomb hit the two-storey house. The owner was frantic.

US officials had no immediate details.

Guerrillas have grown increasingly bold in launching mortar attacks in the past week on the US-led administration on the West side of the Tigris

The attacks have not killed anyone but have wounded several personnel in the coalition.

Attacks on U.S. troops have left 150 dead in Iraq since President George W. Bush declared major combat over onthe first of May.