A missile fired from a suspected unmanned U.S. plane slammed into a car in a Pakistani tribal region close to the Afghan border on Monday, killing four people, intelligence officials and residents said.

The apparent American strike was the latest of more than 50 in the region since last year aimed at killing top al-Qaeda and Taliban leaders. Last month, the head of the Pakistani Taliban was killed in one such strike.

Monday’s attack took place about 3 km from the town of Mir Ali in North Waziristan, killing four people, two officials and witnesses said. The officials spoke on condition of anonymity, saying they need to remain unnamed to do their job effectively.

The identities of the victims were not known.

Witnesses Ikramullah Khan and Mohammad Salim said the missile hit a vehicle with blacked-out windows — a style associated with Taliban fighters in the region.

Pakistan protests the U.S. missile strikes as violations of its sovereignty and say they fan support for the insurgents, but Washington has shown no sign of abandoning a tactic that it says has killed several ranking militants and disrupted their operations.

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