Thousands of people have begun to flee their homes in Lower Dir
Pakistan has launched air strikes against suspected Taleban hideouts in Buner district, less than 100km (67 miles) from the capital, Islamabad.
The aerial attack in Buner comes as tens of thousands of people have fled their homes in Lower Dir, another area which is seeing heavy fighting.
Hundreds of militants have moved into adjacent regions recently from the Swat Valley, an area they largely control.
Western politicians have expressed concern over Taleban activity there.
The air force's move into Buner marks a widening of the government's offensive against the Taleban.
Military spokesman Athar Abbas said their mission in Buner was to "eliminate and expel" the Taleban from the district.
Maj Gen Abbas said there were about 450 to 500 militants in Buner, in breach of a peace agreement between the government and the Taleban.
Last Friday the Taleban announced they were withdrawing from Buner and have said that there are few fighters left.
Meanwhile in Dir, Gen Abbas said the military had killed about 75 militants since Sunday and described the operation as a success.
The BBC's Mark Dummett in Islamabad says the government is complaining that the militants are trying to take over the areas bordering the Swat Valley.
The Taleban denies the government claims.
In Swat itself the Taleban have now spread northwards.
A peace deal between the two sides this year allowed Sharia law to be adopted in large parts of the region in return for the Taleban laying down arms.
Western politicians - particularly in the US - were highly critical of the agreement.
US Secretary of State Hillary Clinton said the Pakistani government was "basically abdicating to the Taleban and the extremists".
Both the Taleban and the government say they remain committed to the peace deal, which was designed to end a bloody 18-month insurgency.
But the Taleban says it has suspended talks with the government because of the military action in Lower Dir.