(Reuters) - A U.S. drone strike killed four suspected militants in Pakistan's North Waziristan tribal region near the Afghan border on Sunday, intelligence officials and witnesses said, the first strike in almost a month.

The controversial drone program, a key element in U.S. counter-terrorism efforts, is highly unpopular in Pakistan, where it is considered a violation of sovereignty which causes many civilian casualties.

A Pakistani parliamentary committee recently demanded an end to drone strikes on Pakistani territory as part of its recommendations for how its relationship with Washington should change. The United States has given no indication it intends to halt the campaign.

The remotely piloted aircraft targeted an abandoned girls' high school building used by militants in Miranshah, the main town in North Waziristan, the officials and witnesses said. Three militants were wounded.

We intercepted internal conversation of the militants asking for arranging four coffins for the slain men in the drone attack. We don't know about their identity and nationality but those living in the girls' school were mostly Arabs, a security official said.

A local resident, Haji Niamat Khan, said more than two dozen militants were living in the school when it was attacked.

The last drone strike, on March 30, killed four suspected militants and wounded three in the same town of Miranshah, a known hotbed for Pakistan Taliban and foreign militants.

The strikes are a major stumbling block in restoring ties with Washington, badly frayed after an inadvertent cross-border attack by NATO aircraft on Nov 26 last year killed 24 Pakistani troops.

The United States says the strikes in Pakistan's unruly northwestern tribal regions along the Afghan border are very accurate and there is minimal collateral damage.

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