Pakistan's military on Monday killed 23 militants in air strikes on hideouts in the country's restive northwest, where the army has launched an offensive against Taliban insurgents, officials said.

Pakistan began a long-awaited push to clear militant bases from North Waziristan, which borders Afghanistan, in June after a bloody attack on Karachi airport finally sank faltering peace talks with the rebels.

Air strikes, artillery, mortars and ground troops have been used to retake territory in the tribal area, which had become a haven for fighters with the Tehreek-e-Taliban Pakistan (TTP) and other militant outfits.

"23 militants were killed in precise aerial strikes on terorist hideouts in Bangidar area of Ghulam Khan in North Waziristan," a security official told AFP in a text message.

The military says the major towns of Miranshah and Mir Ali have now been cleared of insurgents, along with a strategically important 90-kilometre (55-mile) road through North Waziristan.

But scattered attacks on Pakistani forces in the area continue.

On Monday militants raided a checkpost in the town of Hangu, in the neighbouring province of Khyber Pakhtunkhwa, shooting four people dead including three policemen.

"At least four militants riding a car stopped at a police check post and three of them opened fire killing three policemen and a passer-by," district police chief Anwar Saeed Kundi told AFP.

Nobody has claimed responsibility for the attack so far but Taliban insurgents have waged war against the state in the restive northwest, targeting government installations and killing civilians and security personnel.

Separately, two soldiers were killed and another wounded by a bomb targeting a military convoy in Speenwam area on the border between North Waziristan and the town of Bannu on Sunday, security officials said.

The semi-autonomous tribal areas on the Afghan border have for years been a hideout for Islamist militants of all stripes -- including Al-Qaeda and the homegrown TTP as well as foreign fighters such as Uzbeks and Uighurs.

Washington pressed Islamabad for years to take action to wipe out rebel sanctuaries in North Waziristan, which militants have used to launch attacks on NATO forces in Afghanistan.

The Pakistani army says it has killed more than a thousand militants and lost 86 soldiers since the start of the operation.