The victims had bullet wounds and were dumped in Mohmand tribal area where Taliban forces are active and frequently target security forces and civilians.
"A severely injured man was also found with the victims and has been shifted to a medical facility in Peshawar, the provincial capital," an official said.
Peace committees have been set up in tribal areas to help government deal with rebels but they are ruthlessly attacked by the militants.
Unidentified gunmen had killed a key member of a similar committee in Swat on Thursday.
Government launched a peace process in January but so far official efforts have not yet succeeded.