The gunmen who carried out the ambush in the Bagan area of the Kurram tribal region also kidnapped 18 people from the bus, said Javid Khan, a local administrator. The attack was the latest blow to the peace deal, which was meant to end a four-year conflict that cost hundreds of lives, but has failed to extinguish violence in the area.

The bus was attacked as it was traveling on the main road that runs through Kurram that connects the main town in the region, Parachinar, with Peshawar, the capital of nearby Khyber Pakhtunwkha province, said Khan.

Violence had kept the road closed until the peace deal was struck in February.

Five people were wounded in the attack, said Khan. 

A similar attack killed nine people in mid-March who were traveling on the road from Parachinar.