The clash broke out when the security personnel were conducting an operation in Zao Kharmatang area in Khyber Agency last night.
The security forces engaged in a gunbattle with the terrorists in which 15 militants and four security personnel were killed, officials said.
The operation named Khyber-2 was launched yesterday to clear the area of terrorists and criminal hideouts. Troops have so far cleared Surgarh and Shergarh heights.
Two hideouts of terrorists were also destroyed in the operation.
