In one of Pakistan's deadliest attacks in recent years, a suicide bomber blew himself up in a packed mosque Friday, killing at least 50 worshipers and injuring more than 100 in Pakistan’s tribal belt of Khyber.

Around 400 tribesmen were at the main Madina Mosque in Jamrod performing Friday prayers when the bomber detonated his bomb. The explosion caused the roof of the mosque to collapse, burying many of the worshipers.

“I was offering prayers when the blast hit us. I fell unconscious and when regained consciousness I could only see clouds of smoke, dead and injured around me," says Hashmat Ullah Kooki Khel, a witness the Monitor reached by phone.

Most of the victims belong to THE Kookikhel tribe that is largely considered to pro-government and anti-Taliban. The Pakistani Taliban has not claimed responsibility but officials have blamed the militants for the bombing.

“This is [a] cowardly attack by Taliban and the attackers cannot be Muslims to kill innocent worshipers in the holy month of Ramadan,” Mian Iftikhar Hussain, information minister of Khyber Pakhtoon Khawa province, told reporters. During the month-long holiday, Muslims all over the world observe fasting and offer special prayers.

“They are weakened and the operations by security forces have broken their backbone, so it could be [a] revenge tactic,” Mr. Hussain said.

The Khyber region has great strategic importance as it borders Afghanistan and is a gateway for NATO supplies to US-led forces in Afghanistan.

The area is known as being a hotbed of militants from Ansar-ul-Islam and Lashkar-e-Islam. Lashkar-e-Islam (Army of Islam) is headed by militant commander Manghal Bagh, while its rival Ansar-ul-Islam operates under Qazi Mohib. Both groups are fighting against Pakistani forces in Khyber.

The rivals have a long history of fighting, which has claimed hundreds of lives. Pakistan’s military launched a crackdown in 2009 to clear the region of militants.

In the past, Taliban militants and their allied groups have attacked at mosques and assemblies of tribesmen, known as jirgas, attended by anti-Taliban militias in Pakistan’s northwest.

Last year, the Taliban carried out twin suicide attacks in the village of Darra Adam Khel, where local tribesmen were resisting Taliban influence. More than 60 people were killed in that attack.

About 150,000 Pakistani troops have been deployed in the semiautonomous mountainous tribal belt and have been fighting Al Qaeda and Taliban militants along Afghanistan border. In retaliation, the Taliban have carried out deadly attacks in several cities across Pakistan.