"We saw damaged vehicles on the side of the road that were hit but we did not witness any bombardment," US national Scott Kerr told AFP in Amman.

Kerr, a 27-year-old from Chicago, was among a group of 14 peace activists from the United States, Britain, Canada, Ireland and South Korea who drove Tuesday out of Baghdad in a three-minibus convoy.

Iraqi Information Minister Mohammad Said al-Sahhaf said on Tuesday that several people were wounded when a US warplane attacked two Iraqi buses carrying foreign volunteers, including Americans.

Sahhaf said the incident took place Monday in the western town of Rutba on the road between Baghdad and neighbouring Jordan.

US military authorities at the Central Command headquarters in Qatar later said they had no evidence of the alleged incident.

On Saturday, however, three human shields were injured in a car accident when their vehicle burst a tyre near Rutba, a member of that convoy told AFP after arriving in Amman.

"Three of the five passengers of the taxi were injured, one of them seriously," said Peggy Gish, a US national, identifying them as a South Korean and two Americans.

Gish said they were treated at the Rutba hospital before continuing the trip to Jordan where one of the US nationals was hospitalised for serious injuries which he sustained in the accident.

On the road between Baghdad and the Jordanian border, Iraqi soldiers are manning roadblocks, said Kerr.

He also insisted that human shields who have returned to Jordan planned on going back to Baghdad, which he said was being "terrorised by the bombardments".

"This is not a legitimate war but an occupation," Kerr said of the US-led campaign to topple President Saddam Hussein.

SPACE.WIRE