The strike in Mohmand region underscored the tenacity of the Islamist uprising in the northwest despite Pakistani army offensives over the last 2 1/2 years. The operations have retaken areas where militants enjoyed safe haven, but authorities have struggled to hold onto the gains.
The tribally administered region is home to thousands of militants staging or supporting attacks on American troops fighting a related insurgency in Afghanistan. It also houses al Qaeda leaders and operatives from around the world plotting attacks on the West.
The United States is squeezing the insurgents with missiles fired from unmanned drones. The frequency of such attacks has surged under the Obama administration. In the most recent strike, seven people were killed Monday in a different part of the tribal area from where the suicide bombing took place, Pakistani intelligence officials said.
The Pakistani army has supported the creation of tribal militias against the militants, but the groups have been ruthlessly attacked. On three separate occasions this year suicide bombers killed more than 65 people attending meetings between officials and tribesmen, who are typically paid for attending.
Security is tight at the gatherings, with attendants frisked well away from the fortified government buildings where they take place. But local police and soldiers are poorly equipped and trained, while suicide bombers - especially when they work in pairs or more - are hard to defend against.
The attackers Monday were wearing the uniforms of local tribal police, allowing one of them to get inside the government compound and blow himself up, said regional political officer Amjad Ali Khan. Seconds later, another militant detonated his explosives at the gate, said Khan, who was attending the meeting.
The dead and wounded included tribal elders, police, political officials and civilians. Two television journalists who were at the compound reporting were also killed, said Shakirullah Jan, president of Mohmand's journalist association.
"There was a deafening sound and it caused a cloud of dust and smoke," said Qalandar Khan, who was being treated for his wounds at a hospital in Peshawar, the largest city in the northwest. "There were dozens on the ground like me, bleeding and crying. I saw body parts scattered in the compound."
The blast destroyed one building, and the shrapnel left dozens of holes in the walls. Amjad Ali Khan said the explosives were wrapped with bullets rather than the usual ball bearings, nails or nuts and bolts. He said this may have made the blasts especially deadly.
Militants have killed more than 1,300 people in attacks across Pakistan this year, most of them civilians. But there have been fewer attacks than last year, perhaps because of the army operations, including one in Mohmand, and the expanded U.S. drone strikes.
"We are not scared of such attacks and will keep on taking these enemies of humanity to task until they disappear from society," said Mian Iftikhar Hussain, information minister of the northwest Khyber Pakhtunkhwa province.
Monday's U.S. missiles were the latest of more than 100 to hit the area this year.
They struck a shop and a vehicle close to the town of Mir Ali in the North Waziristan region, said Pakistani intelligence officials on condition of anonymity because they were not allowed to speak to the media. The identities of the dead were not immediately known.
U.S. officials do not say whom they are targeting, but some of the attacks are believed to have killed midlevel or senior Taliban and al Qaeda figures. Pakistan publicly condemns the missile strikes but secretly supports some of them. Civilians are sometimes said to be among the dead, but some locals say the strikes are very accurate in targeting militants.
Almost all the strikes this year have been in North Waziristan, which has yet to see a Pakistani army offensive.