At least 100 people were wounded in the explosion in Yakaghund village in the Mohmand tribal region.
The bomber came on a motorbike and blew himself up near the gate of the local administrator's office, witnesses said.
Mohmand is part of Pakistan's tribal regions where the Taliban and al-Qaeda have a strong presence.
A Taliban spokesman, Ikramullah Mohmand, said the rebels claimed responsibility for the attack.
Their target was a meeting of local officials and anti-Taliban elders from the Anbar Utmankhel tribe, he said.
The top government administrator of Mohmand region, Amjad Ali, said the attack signified "increasing desperation" on part of the Taliban, whose "space is being restricted by security forces".
The explosion hit a commercial area, destroying vehicles and shops and burying a number of people under the rubble.
It also damaged the wall of a nearby prison, allowing some prisoners to escape.
Witnesses said a large number of people were waiting outside the administrator's office when the explosion took place.
"It appeared as though the bike lost its balance and was about to fall, and just then there was a huge explosion," a soldier who was on duty at the office said.