Pakistan's military said Saturday a full-scale offensive in the northwest has put militants on the back foot following a pledge from President Asif Ali Zardari to eliminate the Taliban. Warplanes pounded rebel hideouts in the Swat valley, an ex-ski resort where up to 15,000 security forces have been deployed under orders to crush extremists in an escalating conflict that has displaced hundreds of thousands. "They are on the run," the army said in a statement, without making clear exactly how much progress it had made in driving militants from their positions. But the statement added that Taliban fighters were "trying to block the exodus of innocent civilians by preventing their departure through coercion, IEDs (improvised explosive devices), road blocks with trees and even (making them) hostages". The military said Friday an air and ground offensive to crush the Taliban in the northwest killed more than 140 militants. It was impossible to confirm the death tolls independently, given ongoing operations across three districts which began late last month when the hardline insurgents advanced to within 100 kilometres (60 miles) of Islamabad. Meanwhile, fresh troops were entering the Malakand district which neighbours Swat valley, a local military official said. People fleeing the area, however, have accused the military of also killing civilians in the fierce bombardment. President Asif Ali Zardari, who is on a state visit to the United States, has pledged to eliminate the Taliban. "This is an offensive -- this is war. If they kill our soldiers, then we do the same," Zardari told PBS public television Friday, during a visit to Washington. Pressed on whether Pakistan's stated goal of "eliminating" militants meant killing them, Zardari replied: "Eliminate means exactly what it means." The UN refugee agency has warned up to one million people have been displaced in northwest Pakistan, with tens of thousands streaming out of Buner, Lower Dir and Swat, registering in camps or sheltering with families.