The clashes came during a two-day operation Sunday and Monday in the Maidan area of Lower Dir, a region bordering the Swat Valley where the army has been wrapping up an offensive against Taliban militants, said Maj. Fazlur Rahman, spokesman for the paramilitary Frontier Corps.

Pakistan's army also said more than 50 militants had been killed in the clashes, but there was no way to independently confirm the casualty figures because the area is closed to journalists.

On Monday, the army reported separate clashes had left 20 people dead, including an officer. The deadliest fighting took place in the northern Swat Valley, where the military said it killed 12 suspected insurgents in a gunbattle near the town of Dardial.

The violence shows security remains fragile in the northwest, even as thousands of refugees head back to Swat as part of a government repatriation program for the roughly 2 million people uprooted by the military campaign there.

Rahman said the operation in Lower Dir had been aimed at clearing pockets of resistance in Maidan, and that those killed included militants who had fled the Swat area during the army's offensive.

Pakistan's military is also preparing a similar campaign in the South Waziristan tribal region targeting the Pakistani Taliban chief, Baitullah Mehsud.

The U.S. supports the operations, saying Islamabad must eliminate militant safe havens for its own stability's sake as well as to lessen the threat those fighters pose to the U.S.-led war in neighboring Afghanistan.

The Swat campaign drove some 2 million people from their homes, according to the United Nations. The military recently declared the region largely cleared of militants, and thousands have been returning home.

On Monday, the government officially closed two camps near the city of Mardan that had housed about 20,000 people, said Mian Iftikhar Hussain, the information minister for North West Frontier Province.