Pakistani airstrikes on Friday killed 20 militants in the country's lawless tribal area bordering Afghanistan, the military said, part of a massive ongoing operation against the Taliban.

The strikes took place in Khyber tribal district where the military began its latest offensive in October 2014 carrying out airstrikes and using artillery, mortars and ground troops.

"Twenty terrorists including some of their important commanders were killed in precise aerial strikes in remote areas of Khyber today," the military said in a statement.

It added there were reports of about 18 militants injured in the strikes.

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.

The army began a major campaign against Taliban and other militant strongholds in the North Waziristan tribal area in June last year.

Authorities have since vowed to intensify operations, using air strikes, artillery and mortars to take back territory both in the border regions and other parts of the country.