At least two people have been critically wounded after soldiers opened fire on them for violating the curfew in Sarai Darpa Khel village near Miranshah, residents said.
A curfew had previously been in place for several years but in reality the military only carried out patrols during the day and remained in their bases at night, allowing militants free movement.
At least ten militants were killed in attacks by Pakistani gunship helicopters in the village of Mir Ali, a local intelligence official in Miranshah said.
Five soldiers were wounded when a roadside IED hit them in Karam Kot village, a suburb of Miranshah, the official added.
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Some 40 percent of the region's population of half a million have already fled, leaving around 300,000 behind, multiple residents told AFP.
Many locals had been pinning their hopes on a rare tribal jirga formed by the district's top elders to negotiate with the authorities and avert a military operation.
But an all-night siege of Karachi airport last week by Taliban and Uzbek militants dashed their hopes, a member of the tribal jirga told AFP, requesting anonymity.
In the district's main town of Miranshah, imams made announcements from mosque loudspeakers asking people to recite from the Koran and pray to God for the safety of those who had remained behind.