Fawad Ali, the assistant administrator, was traveling with police to attend a meeting when their vehicle was struck by the device in the town of Mamoond, some 25km from Khar, the main town of Bajaur on Sunday.
Anwarul Haq, another tribal official, says the device was detonated remotely, and that a search for the perpetrators is under way.
"The official along with his five police guards were hit by the explosion that happened along close to the Afghan border," he said.
"Pakistan is blaming some of the Pakistan banned groups based across Afghanistan for carrying out these deadly attacks."
Armed groups have long operated in the tribal region along the Afghan border, where they attack security forces and those seen as cooperating with the central government.