The gruesome incident occurred in Kohat district, bordering Kurram and Aurakzai tribal agencies, where a team of five Custom Department officials were busy in routine checking of vehicles on Hangu-Kohat road late last night, Kohat police spokesman said.
Unidentified militants riding a car ambushed them at around 11:50 pm (local time) in the limit of city police station, the spokesman said.
Four officials were killed on the spot while two civilians sustained critical bullets wounds and were shifted to hospital, police said.
Pakistan launched a full-scale military offensive in the region in June that was intensified when Taliban gunmen massacred 150 people, including 136 children, in an army-run school here in December.