US military officials said in a statement on Saturday that an Iraqi bystander was killed and another was also seriously injured in the attack.

"Three Task Force Baghdad soldiers were wounded when a vehicle-borne improvised explosive device detonated on their convoy in western Baghdad," the military said.

"The three injured soldiers were medically evacuated to a multi-national forces medical facility."

The explosion occurred around 2:40pm (1140 GMT), sending smoke and flames billowing into the sky.

At a nearby hospital, Dr Qasim Muhammad said that an Iraqi woman had been seriously injured in the explosion.

US troops rushed to cordon off the area, while helicopters buzzed overhead. The blast was only a few hundred metres away from the main checkpoint on the way into the sprawling airport compound.

More explosions

More explosions were heard well into the evening from the direction of Baghdad's fortified Green Zone which houses Iraqi government buildings and the US embassy.

Several explosions were heard 
into the evening on Saturday

It was not immediately clear where the shells hit or whether they caused any damage.

A US military spokesman in the Green Zone said he had heard some explosions but was unable to say where they came from or whether they landed nearby.

Smoke and dust was seen rising from the area where the thuds boomed out across the Iraqi capital at about 7:00pm (1600 GMT), an AFP correspondent said.

The sprawling compound in the centre of Baghdad is a frequent target for mortar attacks.

West of Baghdad three US military vehicles were damaged in separate attacks in Abu Ghraib, west of Baghdad.

Aljazeera received a video showing the attack on one of the vehicles in Khan Dhari area while the second was attacked by rocket-propelled grenades.