Belarus detained 32 people working for a private foreign military group near the capital Minsk on the night of Tuesday to Wednesday. That reported the news agency Belta Wednesday.
The agency did not provide further details. Private military companies are illegal in Belarus, which has a presidential election on August 9.
President Alexandr Lukashenko, a 65-year-old former boss of a Soviet collective farm, faces the most significant challenge facing his government in the Eastern European country.
Anger at his approach to the coronavirus pandemic, the economy and human rights is mounting in the iron-fist-ruled country.
Lukashenko has accused protesters of wanting to overthrow him. Likewise, Russia-backed President of Ukraine Viktor Yanukovych was overturned after the Maidan street protests in 2014.