Officials said foreign fighters hiding out in the tribal areas were the main target of this week’s military operations.

“Security forces fired mortar shells from Miranshah fort on the adjacent areas of Machis camp, Kharwani and Sukhail Wazir on Friday morning, followed by pounding suspected militant hideouts with gunship helicopters,” an intelligence official based in Miranshah told reporters.

Miranshah is the main town of North Waziristan and Machis camp a neighbourhood on its outskirts that was once a camp for Afghan refugees but is now thought to be used by militants.

The official said four suspected militants were killed and later security forces carried out a door-to-door search, arresting five others.

The areas targeted in this week’s action were hubs for the Afghan Mujahideen fighting the Soviets across the border in the 1980s.

Local intelligence officials said foreign militants along with their families have taken refuge there in recent years, including Chechens, Uzbeks, Turkmen, Tajiks and Uygurs.

One senior security official suggested the military was in particular targeting the East Turkestan Islamic Movement (ETIM), a separatist militant outfit blamed for numerous terror attacks in China’s unsettled western region of Xinjiang.

He said the Chinese government had pressed Pakistan to take action against the Uygur separatists who are based in North Waziristan.

“The Chinese authorities had conveyed their message separately to the prime minister and the army chief, the issue had been raised even with the president when he was on an official visit to China,” he said.

The military action comes after more than three months of stop-start peace talks between the government and the Tehreek-e-Taliban Pakistan (TTP), which have made little progress since they began in February.

Washington has long pressured Islamabad to carry out an operation to stamp out militant hideouts in North Waziristan, from where they launch attacks against US and Nato troops in Afghanistan.

But it was not clear if the latest military action was the beginning of such an operation. The armed forces carried out similar strikes in January that ended abruptly after a few days.

There have been a number of insurgent attacks on security forces in recent weeks and the air raids and the current strikes fit a pattern of the armed forces responding by hitting the insurgents’ bases in the tribal areas.

Thousands of tribesmen have reportedly fled the fighting in North Waziristan and some complained the army’s offensive had hit numerous civilians.

Grocer Rabbani Khan, 42, said his wife was badly wounded when the shelling began in a blast in the early hours of the morning.

“The army is killing the common people instead of the terrorists,” he said in the town of Bannu, in Khyber Pakhtunkhwa province.

“If the army is serious in getting rid of the foreigners why don’t they carry out a ground offensive after announcing it so that we can leave the area?”

Another man fleeing the offensive, Nasrullah, accused the army of killing civilians.

“The government says it has killed terrorists, we will dig out the graves of our loved ones and hand over the dead bodies to the government to prove they were not terrorists,” he said.

Independent verification of the number and identity of those killed was not possible because the tribal areas are off-limits to journalists.