NORTH WAZIRISTAN AGENCY - Four suspected militants were killed Friday as the armed forces hit insurgent targets in a third day of action in restive tribal area close to the Afghan border.

The military used mortars and helicopter gunships to pound suspected Taliban hideouts in North Waziristan, one of seven tribal districts where militants have strongholds.

Friday's operation comes after two days of fighting in the area which began on Wednesday with air strikes and ground clashes which left at least 71 suspected militants and four security personnel dead.

Officials said foreign fighters hiding out in the tribal areas were the main target of this week's military operations. Reportedly, the military at the asking of China was particularly targeting a separatist militant outfit blamed for numerous terror attacks in China's restive western region of Xinjiang.

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

Miranshah is the main town of North Waziristan and Machis camp is a neighbourhood on its outskirts which 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.

Our correspondent reported that during last night offensive security forces targeted Degan and Machas camp areas of the agency as they continued their targeted operation with the help of artillery gun and gunship helicopters. More than 70 militants have been killed and dozens of their hideouts demolished in three days of operation.

Government offices and bazaars remained closed on Friday amid an atmosphere of fear. Curfew was relaxed in the area from morning to 5pm however after the curfew was re-imposed in the evening to restrict the movement of the militants.

After relaxation of curfew in Mirali and Miranshah area, thousands of people started migrating toward safer places including Bannu and other settle areas bordering North Waziristan. Local sources said that there was relaxation in one sided curfew from North Waziristan to Bannu and people have started to migrate to safer places.

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, Chinese, Turkmen, Tajiks and Uighurs.

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 restive western region of Xinjiang.

He said the Chinese government had pressed Pakistan to take action against the Uighur 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.

Some of the fleeing tribesmen who spoke to AFP complained that 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. "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.