At least 18 people were killed Tuesday when gunmen opened fire on a bus in mountainous northern district of Kohistan, police said. The bus was carrying passengers from Rawalpindi, the city where the Pakistani army is headquartered, to the northern city of Gilgit. The motive was unclear as Islamist militants are not active in the area, police said. "Armed men hiding on both sides of the road attacked the bus," local police chief Mohammad Ilyas said. "Initial reports said 18 people have died and eight wounded," he added.