The attackers detonated their explosives outside the office of the assistant political agent at Yakaghund village in Mohmand Agency, 40 km north of Peshawar.
Hundreds of people, including members of an anti-Taliban militia, were present outside the office and in the nearby market, witnesses said.
Political Agent Amjad Ali Khan, the region's top government official, told PTI that 65 people were killed and 112 others injured in the attack. The first bomber was on a motorcycle while the second was driving an explosives-laden vehicle, Khan said.
The Mohmand chapter of the Tehrik-e-Taliban Pakistan claimed responsibility for the attack, one of the worst terrorist assaults in the tribal belt.
Taliban spokesman Ikramullah Mohmand told reporters that the bombers had targeted the political administration and the "peace committee" or anti-Taliban militia from Ambar area because they had organised a jirga against the militants.
Over 60 injured people were being treated at the state-run Lady Reading Hospital in Peshawar and eight of them were in a serious condition, said Abdul Hamid Afridi, the chief executive of the hospital.
Four persons also succumbed to their injuries, he said. Women, children and personnel of the Khasadar militia were among the dead and injured.
Assistant Political Agent Rasool Khan, who office was targeted, escaped unhurt. One of the explosions was not very powerful while the other caused most of the damage, witnesses said.
A prison, some other government offices and over 70 shops were damaged by the blasts. Police said nearly 30 criminals held in the prison escaped during the chaos in the wake of the attack.
Several buildings, including three restaurants, collapsed and footage on television showed people digging through the rubble with their hands.
Security forces cordoned off the area as rescue workers cleared the rubble and removed the bodies and the injured. Ambulances and heavy machinery were sent to Yakaghund from Peshawar to help the rescue operations.