An American citizen was kidnapped near the town of Birnin Konni in southern Niger in the early hours of Tuesday, three security sources and an official said, but no group immediately claimed responsibility.
Details of the kidnapping, on the border with Nigeria, were not immediately clear.
Niger, like much of West Africa's Sahel region, is struggling with a deepening security crisis as groups with links to al Qaeda and Islamic State carry out attacks on the army and civilians, despite help from French and U.S. forces.
Four U.S. soldiers were killed in an ambush there in 2017, sparking a national debate about America's role fighting Islamists in the sparsely populated West African desert that is home to some of the world's poorest countries.
Attacks in Niger, like the one on the U.S. forces, have generally been restricted to a western zone bordering Mali and Burkina Faso, but there have been signs of encroachment this year.
In August, gunmen on motorcycles killed six French aid workers, a Nigerian guide and a driver in a giraffe reserve just 65 km (40 miles) from the capital Niamey.
Birnin Konni, where the sources say the U.S. citizen was taken around 0100 local time (midnight GMT), is a few hundred miles to the east of that region. It is also hundreds of miles from a region of south east Niger that has come under attack from Boko Haram militants based in Nigeria.
Kidnappings in the region are infrequent but not rare. At least six foreign hostages are being held by Islamist insurgents in Mali, Burkina Faso and Niger.
Two of these were taken in Niger, including U.S. aid worker Jeffery Woodke, who has been missing since October 2016, and Joerg Lange, a German aid worker who was taken in April 2018 from a town near the Malian border.