Pakistani air strikes on Saturday killed at least 44 militants in the country's lawless tribal areas bordering Afghanistan, the military said, part of a massive operation against the Taliban.

In Khyber district's Tirah valley where troops are battling Taliban militants and Islamist groups, air strikes killed 28 militants, the military said in a statement.

While in North Waziristan, another northwestern tribal district bordering Afghanistan and a Taliban stronghold, air strikes killed 16 militants, it added.

The military began its latest offensive in Khyber in October 2014 carrying out airstrikes and using artillery, mortars and ground troops.

The Tirah valley is considered a stronghold of Tehreek-e-Taliban Pakistan (TTP) and other militant groups.

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.

Pakistan has been battling a homegrown Islamist insurgency for over a decade following the late 2001 US-led invasion of Afghanistan, though the fighting has at times proved unpopular among those who believe Muslims should not wage war on their co-religionists.

Public opinion however has shifted heavily against the Taliban in recent times after a series of brazen attacks on civilian targets, including a school in Peshawar where more than 150 people -- mostly children -- were killed.

Most of the fighting is now concentrated in the tribal districts of North Waziristan and Khyber.

The Pakistan army has been waging a major campaign against Taliban and other militant strongholds in the North Waziristan tribal area since June last year.