At least six people were killed and two others injured when unidentified gunmen ambushed a private vehicle carrying civilians and army personnel in Pakistan's southwestern Balochistan province on Sunday, police and hospital sources said. Officer Abdul Majeed told Deutsche Presse-Agentur dpa that a Suzuki pick-up was taking passengers from the military camp area of Khuzdar, some 330 kilometers south-east of provincial capital Quetta, to the main market early Sunday when armed men opened fire on it. Majeed feared most of the victims were army personnel. "I can't say exactly, but believe most of the dead would be from the armed forces," he said. Fruit, food and grocery markets are located in the civilian area of Khuzdar, so most of the camp's residents go there on days off for cheaper shopping. On Saturday, at least four people were killed in clashes between police and rioters after local tribesmen protesting the arrest of a tribal leader tried to block roads in Chaman. The city lies on the Pakistan-Afghan border where unidentified men last week set fire to six tankers carrying gasoline from the southern port city of Karachi for the American troops based in Afghanistan's southern Kandahar province.