Gunmen opened fire Sunday on a U.S. convoy on a Baghdad (search) highway, setting one vehicle ablaze, and witnesses said three foreigners were wounded.

The convoy of a military Humvee and two sport utility vehicles, the sort used by American civilians and officials in Iraq, was on a highway in western Baghdad when the gunmen attacked, hitting one of the SUVs.

Witnesses said they heard gunfire and afterward saw American soldiers pulling three wounded people from the stricken vehicle. The witnesses could not tell if the casualties were dead or alive.

The SUV was seen still burning later, its hood pockmarked with bullet holes.

Insurgents, thought to be Saddam Hussein (searchloyalists and foreign fighters, have been waging a campaign of violence against U.S. troops and their Iraqi allies.