At least eight children were among those killed on New Year's Day, when a militant drove a pick-up packed with 550lbs of explosives into a village volleyball tournament being watched by around 300 people.
As rescuers yesterday continued to look for bodies in the rubble, a police spokesman put the official death toll at 88, including the children, two police officers and six paramilitary troops. Another 50 people were injured.
Analysts last night said they believed the attack was aimed at tribal leaders who have formed militias to fend off Taleban insurgents in the northwestern region, close to the troubled border with Afghanistan.
It was carried out in the village of Shah Hasan Khel, on the outskirts of the city of Lakki Marwat in Pakistan's north-west. Police believe the actual target was a New Year's Day meeting of anti-Taleban militia close to the volleyball field.
Lakki Marwat district is near South Waziristan, a tribal region where the army has been battling the al-Qaeda-backed Taleban since October.
This military operation has been undertaken with the backing of the US, which is eager for Pakistan to free its tribal belt of militants believed to be involved in attacks on Nato troops in Afghanistan. The offensive has provoked apparent reprisal attacks that had already killed more than 500 people in Pakistan before Friday's blast, including an October explosion in Peshawar which killed 112.
Militants have struck all across the nuclear-armed country, and they appear increasingly willing to hit groups beyond security forces. No-one claimed responsibility for Friday's blast, but that is not uncommon when many civilians are killed.
Across Pakistan's north-west, where the police force is thin, underpaid and under-equipped, various tribes have taken security into their own hands over the past two years by setting up citizen militias to fend off the Taleban. The government has encouraged such "lashkars," and in some areas they have proven key to reducing militant activity.
Several suicide attacks have targeted meetings of anti-Taleban elders. Militants have killed so many tribal leaders they have created a power vacuum, which they now exploit.
Shah Hasan Khel village "has been a hub of militants. Locals set up a militia and expelled the militants from this area. This attack seems to be reaction to their expulsion," local police chief Ayub Khan said.
Mohammed Qayyum, 22, yesterday held back tears as he told how his younger brother died when the explosion destroyed his family's mud-brick home and three dozen others. "After the blast, I heard cries, I saw dust, and I saw injured and dead bodies," said Qayyum, who was unhurt."Everybody was happy before the explosion, but today we are mourning."
Pakistan's prime minister Yousuf Raza Gilani yesterday vowed to defeat militants, saying "the agenda of terrorists is to destabilise the country, to create panic and spread fear".