Pakistan warned the Taliban today it would expand a military offensive to Buner, a district around 100 km (60 miles) northwest of Islamabad, if the guerrillas did not withdraw from the area.
Interior Minister Rehman Malik said around 450 Taliban were reported to have sneaked into Buner yesterday.
"I warn them to vacate the area. We are not going to spare them," he told reporters. "Action will be taken if anyone tries to block our efforts to re-establish writ of the government in Buner and other areas," he said.
Pakistani security forces launched an offensive against militants in the Lower Dir district of North West Frontier Province's Malakand Division on Sunday to stop the militants spreading out of the Swat valley.
Military officials say around 70 militants have been killed in fighting since Sunday. Independent casualty estimates are unavailable.
Buner and Swat are both in Malakand, where President Asif Ali Zardari this month reluctantly agreed to impose Islamic sharia law in a bid to persuade the Taliban in Swat to lay down their arms.
But emboldened by government's concession, Taliban fighters began moving into Buner and nearby Shangla district.