Pakistani forces expanded their offensive in the Taliban stronghold of Swat on Saturday as a humanitarian crisis intensified with thousands of civilians stranded on the battlefield.
The UN's refugee agency has estimated that up to 200,000 people have fled the former tourist haven in recent days.
Pakistani military announced "a full-scale operation" on Friday, the day after Prime Minister Yousuf Raza Gilani called for national unity as the troops were ordered "to eliminate the terrorists".
The US welcomed the military action amid concerns about dwindling stability in the nuclear-armed state, which it considers central to the counter-insurgency efforts in Afghanistan.
Helicopter gunships pounded militant positions in Swat's main town of Mingora on Saturday to soften Taliban resistance as troops pushed forward with the ground operation, a local official said on condition of anonymity.
There were no immediate reports of casualties but several militant hideouts were destroyed in the airborne attacks.
Clashes were also reported in other parts of Swat and the adjoining district of Buner and Lower Dir, but details were not available.
More than 140 Taliban fighters were reported killed on the first day of the all-out offensive, with the troops suffering at least seven casualties. The toll could not be verified independently.
Military spokesman Major General Athar Abbas told reporters that troops were battling up to 5,000 hardcore Taliban militants in the scenic valley, located 140 km northwest of the capital Islamabad.
Officials said the militants were using the residents as "human shield" and preventing them from fleeing the escalating hostility.
An indefinite curfew remained in place in the insurgency-hit areas of Swat, with the authorities saying that the relaxation timings could not be disclosed in advance as the militants could attack non-combatants leaving the valley.
Commentators say there is a wide consensus, at least for now, that the government needs to go all-out against the Taliban, but warn that the situation could change in case of heavy collateral damage and improper rehabilitation of the displaced people.
Pakistani authorities have set up nearly a dozen camps with support from international and local relief agencies. However, UN refugee agency spokesman in Geneva, Ron Redmond, said the new influx would place "huge additional pressure on resources".