A suicide bombing killed more than two dozen people at a mosque during Friday prayers in Pakistan's Mohmand tribal area near the Afghan border, officials said.
More than 30 others were injured in the attack.
The Taliban splinter group Jamaat-ul-Ahrar claimed credit for the attack. The group claimed that the attack targeted members of a resistant tribal militia. It warned members of such militias to "stop opposing Islam and jihad," the Wall Street Journal reported.
The Mohmand area, near the Afghanistan border, is known to have bases for the Taliban and other militant groups.