KABUL—Unidentified militants seized 47 passengers traveling on a highway in Afghanistan’s Kunduz province on Wednesday, officials said, the latest in a series of kidnappings fueling concerns that the government is losing control of major routes.

Armed men seized people from a bus and car after stopping the vehicles on the outskirts of Kunduz city, which was briefly held by the Taliban late last year. The highway connects Kunduz to the neighboring province of Takhar.

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