Amid concerns about the Taliban’s recent advances to the Pakistani capital, the army says its new full-scale offensive is purging the Swat Valley of the insurgents.

After Taliban insurgents fired rockets at a military base in Mingora on Saturday, the army moved to launch a full-scale operation with helicopters targeting Taliban hideouts in the hotly contested areas of the country’s northwest.

Military spokesman Major General Athar Abbas said on Saturday that the security forces had killed 140 militants in the region.

According to the military spokesman, nearly 4,000 militants estimated to be in the Swat Valley were fleeing the military offensive.

“They are on the run and trying to block the exodus of innocent civilians by preventing their departure through coercion,” Athar said.

Other sources in the military claimed to have killed at least 170 insurgents across the valley and its adjoining districts over the past 24 hours.

Meanwhile, fresh troops and military enforcement were sent to the valley and its adjoining areas after earlier on Thursday Premier Yousuf Raza Gilani ordered the army to “eliminate militants and terrorists” battling government forces in the region.

The escalating violence has prompted massive displacement in the insurgency-plagued area.

Red Cross has warned that a major humanitarian crisis is looming in the region, where an estimated half-million people are being displaced.

The US invasion of Afghanistan in 2001 pushed the militants across the border and into Pakistan. Ever since, the restive tribal belt between the two neighbors has become a scene of daily violence.

Islamabad government says it will force the militants to lay down their arms, but the military’s top spokesman, Major General Athar Abbas, said on Friday the operation in Swat was difficult and he declined to give a timeline for clearing the valley.

Pakistan’s President Asif Ali Zardari has vowed to continue the offensive against the Taliban in the Swat region until normalcy is restored to the volatile valley.