Islamabad, Pakistan (CNN) -- A leader of an anti-Taliban militia was killed in a bomb attack in northwest Pakistan on Tuesday, a Pakistani police official told CNN.
The man, Aziz-ur Rehman, his 12-year-old son and two others were killed in the attack, police said.
The bomb exploded as the militia leader was traveling in a car with his son, son-in-law and a neighbor, said Salim Khan Marwat, a local police chief.
The attack took place in a village in Lower Dir, a district where militant groups have increasingly targeted a growing number of pro-government militias that have formed to take on the Pakistani Taliban and other violent extremist groups in the region.
It was not clear who was responsible for Tuesday's attack.
Journalist Nasir Habib contributed to this report.