Five Afghans, three of them working on an opium crop substitution project, were killed yesterday in a Taleban ambush, a provincial official said. The five were traveling in a vehicle in Helmand province, in southern Afghanistan, when gunmen attacked, said provincial official, Muhayuddin Khan. "This was carried out by Taleban insurgents," Khan said. Troops have been sent out to search for the rebels, he said.