Pakistani jet fighters and helicopter gunships began airstrikes in a northwestern tribal district Tuesday, killing more than 20 militants in retaliation for two recent bombings targeting the military, officials said.

The bombardment came a day after a suicide attack in a market next to Pakistan's military headquarters that killed 13 people including eight soldiers and three children.

On Saturday, a vehicle-borne suicide bomb in the restive northwestern city of Bannu killed 26 people, the deadliest attack on Pakistan's military in several years.

Both attacks were claimed by Tehreek-e-Taliban Pakistan (TTP).

The focus of Tuesday's air strikes was North Waziristan tribal district, a stronghold for Taliban and Al-Qaeda linked militants.

Jet fighters began pounding targets around 12:30am (1930 Monday GMT), an official said, and were later joined by helicopter gunships.

"More than 20 militants were killed and at least 15 wounded. Jet fighters also destroyed militant hideouts," a security official told AFP.

The official said "some foreigners and a commander of the Punjabi Taliban were among those killed".

The Punjabi Taliban are a faction of the militant group that hail from the country's largest province in the east.

A government official confirmed the airstrikes and killing.

An intelligence official in Miranshah, the main town of North Waziristan, said the airstrikes and shelling were still going on and had forced some residents of the area to flee.

Independent verification of the casualties was not possible because media and aid workers are not allowed to visit the area.

The TTP have been waging a bloody campaign against the Pakistani state since 2007, carrying out countless bomb and gun attacks, often on military targets.

Two high-profile attacks in two days mark a sharp upturn in violence from the TTP after a period of relative quiet following the death of their leader Hakimullah Mehsud in a US drone strike in November.