SOUTHERN IRAQ (AFP) - Three US troops were wounded , one seriously, after Iraqi soldiers used a Red Crescent ambulance to stage an attack in southern Iraq (news - web sites), an AFP correspondent reported. The Iraqi troops in Monday opened fire on a group of American soldiers who had approached the ambulance at a town north of Nasiriyah. The seriously injured soldier would be evacuated, while two others were undergoing surgery at a captured air base, a US air force source said.