The militants attacked the vehicle at a spot about 20 km from Tank. The six persons in the car were injured in the firing. One of them, Shafi Ullah, succumbed to his injuries while being taken to hospital, police said.
Shafi Ullah and the injured persons were all members of a peace committee or an anti-Taliban militia that had battled militants in the past.
The Pakistani Taliban have killed scores of pro-government tribesmen and elders in attacks across the restive northwest in the past few years.