ISLAMABAD (Reuters) -- A bomb blast has killed around 40 worshippers attending Friday prayers at a mosque in a remote area of northwest Pakistan, a senior official told Reuters.
"Around 40 people are killed. The death toll is 40. We have no idea as yet how many have been wounded," Atif-ur-Rehman, the senior-most government administrator in Upper Dir, where the explosion occured, said.
Upper Dir is close to Swat valley where Pakistani security forces launched a major offensive last month to expel Taliban militants.
Pakistani officials have warned that militants would strike back.
U.S. special envoy Richard Holbrooke was due to hold talks the same day as the attack with army chief General Ashfaq Kayani.
Dir's blast is the ninth bomb attack in the country since the offensive began, and the Taliban has threatened more revenge.