At least two Pakistani security-force members were killed when their vehicle struck a roadside bomb in a restive northwestern region.
Officials said the bomb exploded on February 3 in the Warmagai village in the Kurram Tribal Agency.
An official said security forces killed two militants during a search operation carried out after the bombing.
Tribal areas bordering Afghanistan became a hideout for Islamist militants in the aftermath of the U.S.-led invasion of Afghanistan in 2001.
Pakistan began an offensive to clear militants from North Waziristan in June 2014.
The military intensified its offensive after Taliban fighters seized a military-run school in the northern city of Peshawar on December 16 and killed 151 people, almost all of them children.
