The bombing took place in the village of Butmana in the Mohmand tribal district bordering Afghanistan where the army has been fighting against Taliban militants.
“The Friday prayer was in progress at the mosque when a suicide bomber blew himself up killing at least 16 worshippers and wounding 35 others,” a senior tribal administration official told AFP.
“The area is remote and so far I have received only this information from our sources via wireless,” he said.
Another local government official confirmed the information.
There was no immediate claim of responsibility, but Pakistani Taliban in particular routinely attack soft targets such as courts, schools and mosques.
Taliban militants stormed a school in Peshawar in December 2014, killing more than 150 people, mostly children, in Pakistan’s deadliest-ever terror attack.
The army launched an operation in June 2014 in a bid to wipe out militant bases in the northwestern tribal areas and so bring an end to the bloody insurgency that has cost thousands of civilian lives since 2004.
Security in the country has since improved. Scattered attacks still take place, but they are fewer and of a lesser intensity than in previous years.