A suicide bomber detonated his explosives-packed vehicle in a crowd of people watching a volleyball tournament in northwest Pakistan, killing 88 people in the deadliest attack in the country in more than two months. The attack in Lakki Marwat city on Friday appeared to be retaliation against residents who formed militias to drive militants out of the area and a meeting of anti-Taliban leaders being held nearby may have been the actual target, police said. The blast underscored the difficulty Pakistan has had in stopping militants whose reach extends far beyond Pakistan's lawless tribal belt and who appear increasingly willing to strike civilians as well as security forces. The attack was not far from South Waziristan, where the army is waging an offensive against the Pakistani Taliban. That operation has provoked apparent reprisal attacks that have killed more than 500 people since October. No group claimed responsibility for Friday's blast, but that is not uncommon when large numbers of civilians are killed. "The locality 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 told reporters. Khan said an anti-Taliban meeting of local tribal elders in a mosque close to the field where the tournament was being held was the real target of the attack, but the driver failed to reach it. The bomber set off some 550 pounds (250 kilograms) of high-intensity explosives loaded in the car at the field, which lies in a congested neighborhood, Khan said. Local police official Tajammal Shah said Saturday that 88 people were dead and 50 wounded. He said eight children, six paramilitary troops and two police were among the dead. Omar Gull, 35, a paramilitary soldier who was wounded, told an AP photographer at a nearby hospital that the attacker drove the vehicle recklessly into the crowd. "People were just trying to understand what's happening when the bomb went off," he said. "It was then chaos. It was smoke, dust and cries." Another police official, Habib Khan, said some 300 people were on the field when the incident took place. "We had security there. We had it for the meeting, and for the tournament," Ayub Khan told The Associated Press by phone. Regional Information Minister Mian Iftikhar Hussain reiterated the government's resolve to target militants wherever they may be, saying "we need to be more offensive to fight them." The attack was the deadliest since a car bomb killed 112 people at a crowded market in Peshawar on Oct. 28. Karachi, the country's largest city, came to a virtual standstill Friday after religious and political leaders called for a general strike to protest a bombing that killed 44 people and subsequent riots. The city's major markets, stores and business centers were closed, along with financial institutions that had already planned to shut for New Year's Day. Public transportation was halted and gas stations were closed. Monday's bombing occurred in the midst of a procession of minority Shi'ite Muslims during the Islamic holy month of Muharram. Afterward, angry protesters went on a rampage, setting fires to about 2,000 stores that took three days to completely put out. Interior Minister Rehman Malik, on a visit to Karachi, said investigators were still determining if the attack was a suicide bombing. He also questioned the claim of a purported Taliban spokesman, Asmatullah Shaheen, that the militant group was behind the attack. Local news reports on Friday quoted a more prominent Taliban spokesman, Azam Tariq, as denying that the Pakistani Taliban's central leadership had approved the attack, though he did not rule out the possibility that Shaheen's group had carried it out without approval. Also Friday, a suspected US missile struck a car carrying alleged militants in North Waziristan tribal region, killing three men, two intelligence officials said. It was the second such strike in less than a day. The strikes are part of the US campaign to eliminate high-value militant targets that use Pakistan as a safe haven to plan attacks in neighboring Afghanistan and on the West. Friday's strike happened near Mir Ali, a major town in the region, two intelligence officials said on condition of anonymity because they were not authorized to speak on the record. Shortly afterward, Taliban fighters arrived at the scene of the attack in the village of Ghundi and moved the bodies to an undisclosed location, the officials said. Thursday's missile strike was also near Mir Ali, hitting a house and killing three people. US officials rarely discuss the strikes, and Pakistan publicly condemns them, though it is widely believed to aid them secretly. Elsewhere in the northwest, a roadside bomb exploded near a car in the Bajur tribal region, killing an anti-Taliban tribal elder and five of his family members, said Nasib Shah, a local government official. Bajur was the focus of a 2008-09 army offensive but still suffers some militant violence. Tribal leaders who support the government against the Taliban are frequent targets of attacks.