A suicide bomber has killed at least 20 people and wounded dozens while they were attending prayers at a mosque in a northwestern Pakistani tribal area, sources tell Al Jazeera.

Friday's bombing occurred in the village of Anbar Tehsil in the Mohmand tribal district bordering Afghanistan where the Pakistani army has been battling the Pakistan Taliban.

"The Friday prayer was in progress at the mosque when a suicide bomber blew himself up," a senior tribal administration official told AFP news agency.

There was no immediate claim of responsibility, but Pakistani Taliban in particular routinely attack soft targets such as courts, schools and mosques.

The army launched an operation in June 2014 in a bid to wipe out armed groups bases in the northwestern tribal areas to bring an end to the insurgency that has cost thousands of civilian lives since 2004.

Source: Al Jazeera News And Agencies