PESHAWAR: At least 21 suspected terrorists were killed Friday in military air strikes in Khyber Agency's Tirah Valley, said security sources.

Pakistan Air Force jets targeted militant hideouts in Koki Khel area of Tirah, killing at least 21 suspected terrorists and razing several hideouts.

Khyber Agency is one of seven semi-autonomous tribal districts where forces have traditionally had little control and militant groups thrive.

The area is off-limits to journalists, making it difficult to independently verify the number and identity of the dead.

Pakistan Army launched Operation Zarb-i-Azb, a grand operation in the North Waziristan tribal region, following a Taliban attack on the Jinnah International Airport in Karachi in June 2014.

Since the beginning of Zarb-i-Azb, militants have fled to other tribal regions, including Khyber and its Tirah Valley and Shawal, all of which border Afghanistan.

After the Dec 2014 carnage at Peshawar's Army Public School, the army and the government intensified operations against militants and their abettors in the country.