High in the mountains along the Afghan border, Pakistan’s fight against Taliban militants is focusing on their last, fearsome redoubt -- the notorious Tirah Valley, home to renegades and rebels for centuries.

High in the mountains along the Afghan border, Pakistan's fight against Taliban militants is focusing on their last, fearsome redoubt -- the notorious Tirah Valley, home to renegades and rebels for centuries.

The military has mounted a series of air strikes and ground assaults in Tirah in recent weeks that it says have captured key passes in a remote region that has never before come under full government control.

The operation in Tirah, part of Khyber tribal area, aims to build on the army's offensive against strongholds of Tehreek-e-Taliban Pakistan (TTP) and other militant groups in nearby North Waziristan that began in June last year.

Last month the army said it killed at least 230 militants in Tirah, which has long been a hideout for TTP ally Lashkar-e-Islam (LI).

Security officials in the northwest told AFP that the so-called Khyber II operation to shut down LI's hideouts in Tirah began in earnest on March 18, and ground skirmishes are continuing.

Chief military spokesman Major General Asim Bajwa tweeted last week that the strategic Masatul pass, which links to Afghanistan's restive Nangarhar province, had been secured.

A security source in the northwest said other important passes had also been taken.

"We have taken over three main strategic locations by moving ground forces to Masatul Pass, Takhtakai mountain and Sokh area," one security source told AFP.

"With these gains, we have blocked their movement from and to Orakzai tribal region, Kurram, Bara and Afghanistan."

The area is remote and off-limits to journalists, making it difficult to verify the army's claims -- and the number and identity of those killed.

TTP spokesman Muhammad Khurasani denied the claims, saying his group has killed 30 soldiers so far and lost only three militants.