A Swiss citizen working on a U.S.-funded aid project has been arrested in Burkina Faso, the Federal Department of Foreign Affairs in Switzerland and a foreign official said on Tuesday.

The motive for the arrest was not immediately clear.

"The FDFA is aware of the arrest of a Swiss citizen in Burkina Faso," the foreign affairs department said in a statement.

It was not immediately possible to reach Burkina Faso's ruling military junta for comment on the arrest.

Burkina Faso, located in the sub-Saharan region known as the Sahel, has experienced two coups in recent years. Relations between the authorities and Western powers have grown increasingly strained.

On Monday, Denmark said it was closing its embassies in Mali and Burkina Faso. This followed Mali's move to expel Sweden's ambassador earlier this month following a diplomatic dispute.

A foreign official focused on Sahel issues said the Swiss citizen was working on a U.S.-funded aid project in Niger and Burkina Faso as the chief of party for U.S.-based nonprofit Winrock International.

He was first detained in Niger, alongside a British citizen. Both were released. The Swiss citizen then traveled to Burkina Faso, where he was arrested and detained, the foreign official said.

Winrock International has domestic offices in Arkansas and Virginia. The organization works on water security and resilience in Burkina Faso and Niger, according to its website.

Winrock did not respond to requests for comment.

Burkina Faso's army is fighting a jihadist insurgency that has spread across the Sahel region south of the Sahara since it first took root 12 years ago. The worsening violence in the region has also led to two coups in Mali and in neighbouring Niger since 2020.

Burkina's junta, which seized power in a 2022 coup, is accused of suppressing dissent by kidnapping and conscripting critics and urging citizens to report suspicious neighbours in the name of national security.