Sunday's attack is Pakistan's third suicide bombing in as many days
Scores of people were hurt in the blast, near the town of Dara Adam Khel.
Officials say that the blast happened as the elders were discussing the security situation in the area.
The town, which is 40km (25 miles) south of the city of Peshawar, was the scene of fierce clashes between troops and militants in January.
At least 13 troops and 70 militants were killed after militants occupied a Japanese-built road tunnel.
Correspondents say the border areas of North West Frontier Province are a hotbed of militancy and a feeding ground for the Taleban and al-Qaeda, and have seen growing violence directed at Pakistani government forces.
But Islamists were beaten by secular parties in the tribal regions and in neighbouring North West Frontier Province in the recent parliamentary elections.
Body parts
The attack took place when tribal elders and officials had gathered for a traditional jirga, or assembly, to discuss increased Taleban activity in the area.
They had just finished their discussions when the bomb went off, local official Khalid Khan told AFP news agency.
Reports said a young man went up to the elders and blew himself up.
"It was a huge explosion and left body parts and blood scattered on the ground," Ramin Khan, who was injured in the blast, told the Associated Press news agency.
Doctors said many of the injured were in a critical condition and the death toll could rise.
It is the third attack in as many days in north-west Pakistan. On Friday, a suicide bomber attacked a funeral in the troubled Swat valley, killing at least 38 people.
A bomb in Pakistan has killed at least 40 people and injured several more. The attack took place on the outskirts of Dara Adamkhel, a town which is close to the border with Afghanistan. It has been reported that the bombing may have been a suicide attack, although that has not yet been confirmed.

A Pakistani official at the scene said that "at this point, we the Pakistani government have reports of over 40 dead and scores of wounded." The Pakistani Interior Ministry spokesman said that "we the Interior Ministry are trying to get information. Initial reports suggest it was suicide attack."

The bomb exploded during a jirga, or tribal meeting, regarding security in the northwestern Pakistani town.

Dara Adamkhel is located about 40 km away from Peshawar, the provincial capital.