Local TV channel ARY reported that the explosion happened in the restive Tirah Valley area of Khyber Agency at about 3:30 p.m. local time, when some unknown militants targeted the camp of pro- government local people who formed a militia to fight the militants in the area.
Nature of the blast is not known yet.
The injured people were shifted to a nearby hospital where several of them were said to be critical.
No group claimed responsibility for the attack yet.
Early in the morning, one soldier and 15 militants were killed in clashes between insurgents and security forces in the same area.
Tirah valley is a strategically important area to both Pakistan army and militants, as some of the major roads from the valley lead to Afghanistan.
The fighting between militants and troops has been underway in the area since last year, however, the clashes escalated during last month when militants took hold of some of the major areas.
Local officials said that over 40,000 residents of Tirah Valley have taken refuge in the nearby areas due to the continuous clashes between different militant organizations and army over the last few months.