Government helicopter gunships killed 52 Islamist militants Friday in two attacks in northwestern Pakistan, a lawless region where Al Qaeda and Taliban militants increasingly hold sway, a government official said.

The attacks took place close to the Khyber region, said Fazal Mahmood, the No. 2 government representative in the area.

They destroyed five militant hide-outs, a large ammunition depot and eight vehicles, he said.

It was not possible to independently verify his account because the region is very dangerous to visit.

Militants have stepped up attacks in the Khyber region in recent months, seeking to disrupt a vital supply line for Western forces in neighboring Afghanistan.

Earlier, hundreds of Shiite Muslims angered over a bloody suicide attack outside a mosque burned a police station in central Pakistan, police and witnesses said.

City police Chief Maqsood Ahmed said the protesters also damaged some shops and disrupted traffic in various parts of the city of Dera Ghazi Khan by burning tires.

Ahmed said the protesters were demanding the arrest of those who orchestrated the attack late Thursday, and that officers were seeking help from Shiite leaders to restore order.

The violence came hours before the funerals for at least 27 people who died in the blast, which occurred as a crowd streamed into a Shiite mosque for an evening prayer ceremony. No one claimed responsibility for the bombing.

Authorities usually blame extremist Sunni militant groups for such attacks. Although most of Pakistan's majority Sunni and minority Shiites live peacefully, extremists on both sides often target each other's leaders, and Shiite rallies and places of worship are often attacked.

Meanwhile, suspected militants shot and killed two alleged U.S. spies in Miran Shah, the main town in the North Waziristan tribal region near Afghanistan, said Tahir Khan, a tribal police official.

Khan said the bodies were spotted early Friday. Both men were identified as Pakistanis, with notes pinned to their bodies that warned others to learn a lesson from their fate, he said.

Insurgents have killed nearly two dozen suspected U.S. spies in recent months.

Meanwhile, the Islamabad High Court freed disgraced nuclear scientist Abdul Qadeer Khan on Friday from years of de facto house arrest. Khan, the architect of Pakistan's nuclear program, allegedly supplied nuclear secrets to countries including Iran, North Korea and Libya.

Khan took sole responsibility in 2004 for leaking the nuclear secrets but was immediately pardoned by former President Pervez Musharraf and placed under a form of house arrest.

Government prosecutor Amjad Iqbal Qureshi said the court order was the result of a compromise and that "security measures" for Khan would remain, suggesting that authorities may still limit his movement. The government has never said that Khan was under house arrest, maintaining he was subject to extra security for his own safety.

A pariah in the West, Khan is lionized by conservatives and Islamist hard-liners for making Pakistan the world's only Muslim nuclear power and is a hero to many ordinary citizens.