The incident took place in Safi area of Mohmand Agency and the death toll is likely to rise.
According to local tribesmen, the first blast targeted the peace committee members, who were riding a motorcycle, with a remote-controlled IED. The second explosion took place when the bodies and injured from the first blast were being evacuated, the Dawn reported.
The injured have been shifted to the hospital.
Security and rescue teams reached the blast site and cordoned off the area as a probe into the incident went underway.
Pakistan's military has been fighting to eradicate militants in the tribal area.
They have launched the latest Operation Khyber-I amidst Zarb-i-Azb, a full-fledged military operation being conducted by the army against Tehreek-i-Taliban Pakistan (TTP) and other militants in the tribal region.