The killings come amid reports of a suicide blast, also in the northeast.
At least three people have been killed in the blast in the Charsadda district, Al Jazeera has learned.
The bomber rammed his explosives-laden vehicle into the gates of a school in the Subhan Khaur village.
The school was not occupied by any children, but was being used by security forces battling pro-Taliban fighters in the region.
"At least three paramilitary soldiers have been killed in the suicide attack," said Marjan Ali, a police official.
"It was a large vehicle. Body parts of the suicide bomber and the wreckage of the vehicle was scattered on the site."
Subhan Khaur borders the Mehmand district, one of seven tribal areas bordering Afghanistan.