A suicide car-bomber killed 24 Pakistani paramilitary soldiers and wounded 29 on Saturday in an attack that may be linked to an army assault on a radical mosque in the capital, a military spokesman said.
The attacker rammed his car into a paramilitary convoy in the North Waziristan region on the Afghan border, 20 km southeast of its main town of Miranshah.
It was the second attack on security forces in northwestern Pakistan on Saturday. Two security officials were wounded in an earlier blast near the town of Bannu in North West Frontier Province.
The attacks followed the storming of a radical mosque in Islamabad on Tuesday in which 75 supporters of hardline clerics, most of them militant gunmen, were killed.
"We can't say for sure but it could be a reaction to that," military spokesman Major-General Waheed Arshad said of the North Waziristan blast when asked if it might be linked to the mosque assault.
Nearly 50 people have been killed in bomb attacks targeting troops and police in the northwest since July 3, when security forces in Islamabad surrounded the Lal Masjid, or Red Mosque, complex, following clashes with gunmen based there.
At least one wanted militant, speaking before commandos stormed the mosque, had threatened to launch revenge attacks if the mosque was assaulted.
Many of the militants who turned the mosque-school complex into a virtual fortress, and many of the religious students who studied there, were believed to have been from the northwest.
It was the most serious attack on Pakistani security forces since November when a suicide bomber killed 42 army recruits on a training ground in the northwestern town of Dargai.
In a separate incident on Saturday, authorities in the northwestern city of Peshawar discovered two anti-tank mines hooked up to a timer in a car abandoned on a main city street. It was safely dismantled.
Last Sunday, three Chinese workers were shot dead in Peshawar in an attack police said appeared to be linked to the Lal Masjid.
Protesters angry about the assault on the mosque have ransacked offices and looted supplies of Western aid agencies in various parts of North West Frontier Province.
The government has sent extra troops to at least four different parts of the province, a provincial official said.
The army said 75 people had been killed in the assault on the Lal Masjid mosque-religious school complex.
Interior Minister Aftab Ahmed Sherpao said on Friday 60-65 of the dead were militants and four or five of them were foreigners, but he did not say from where.
North Waziristan is a hotbed of al Qaeda and Taliban support, from where Taliban fighters launch raids into Afghanistan, U.S. military officers in Afghanistan say.
U.S. security officials also say al Qaeda members plot violence from sanctuaries in North Waziristan and other lawless regions on the Pakistani side of the border.
The Pakistani government struck a deal with tribal elders in North Waziristan last September aimed at isolating foreign militants. Attacks on Pakistani security forces in the region have been relatively rare since then.