In one attack, a suicide bomber blew himself up as Friday prayers were ending, killing at least 66 people, officials said. The attack occurred in Darra Adam Khel, a suburb of Khyber-Pakhtunkhwa province capital Peshawar.

In the second attack, hand grenades were thrown into a mosque on the outskirts of Peshawar during evening prayers, killing at least five people and wounding 11, officials said.

Earlier state-run PTV announced deaths of 60 people but later officials of Kohat administration  confirmed 66 deaths.

The attack in the volatile northwest was the deadliest in the nuclear-armed country on the front line of the US-led war on Al-Qaeda in two months.

Commissioner Kohat Khalid Omazai told reporters, "Anti-state elements have carried out the attack on a mosque. We were expecting such attacks because military operations by Frontier Corps and Pakistan Army are going on in Orakzai agency."

The mosque's roof collapsed as hundreds of worshippers were gathered inside for the weekly prayers, and many victims were trapped in the debris.

People in private vehicles rushed the wounded to hospitals in Peshawar, the main city in the northwest, TV footage showed. A woman was beating her head, while two elderly men in blood-soaked clothes laid in a hospital corridor.

The explosion occurred in Darra Adam Khel, an area famous for its illegal weapons bazaars and located near Pakistan's tribal regions where Taleban-led militants have been active.

"The blast tossed me up, then I fell down," Mohammad Usman, 32, a schoolteacher with wounds on his head and arms said from his hospital bed in Peshawar. "Later, it was just like a graveyard." Local government official Shahid Ullah said the mosque may have been targeted because local tribesmen running an anti-Taleban militia have often met there, though not on this particular Friday.

The government has encouraged tribal leaders to set up militias to fight the insurgents, and the Taleban have frequently targeted those opponents.

GEO News TV reported that the Pakistani Taleban claimed responsibility for the attack.

Shahid Ullah put the death toll at 60 and said 80 others were wounded. That made it the deadliest since September's suicide bombing on a Shiite procession in the southwest city of Quetta, which killed 65. The Pakistani Taleban claimed responsibility for that strike.

Several shrines and mosques belonging to rival sects hated by the Taleban also have been targeted this year. At least three such attacks occurred in October alone.

Provincial Information Minister Mian Iftikhar Hussain called the militants "beasts" that are lashing out at Pakistan's crackdown against them.

"This is part of international terrorism. America, Pakistan and Afghanistan are the main players, who need to work closely and more aggressively to root out this menace," said Hussain, whose only son was killed by militants earlier this year.

Pakistan is in the midst of multiple offensives against Taleban and linked militants in its northwest, including the tribal areas that border Afghanistan.

The US has praised the offensives, in hopes they will break the backs of at least some of the groups involved in attacks on American and NATO troops in Afghanistan.

However, Pakistan has yet to mount an operation in North Waziristan, the tribal region where the most dangerous groups working against the US in Afghanistan have bases.