The co-workers of a Belarusian journalist and military expert who has been missing for several days say he is in a pretrial detention center in Minsk.
Journalists at the "Belarusians & Market" weekly wrote on December 8 that their colleague Alyaksandr Alesin was arrested on November 25.
Some media reports in Belarus last week said Alesin had been arrested on espionage charges.
Belarusian KGB spokesman Artur Strekh refused on December 5 to comment to RFE/RL on the reports.
The Minsk-based Vyasna (Spring) human rights center and the Association of Belarusian Journalists have urged authorities to give information about Alesin's arrest.
Alesin is a leading military expert whose comments often contradict government positions.
Alesin recently said Belarus should reform its army in light of the crisis in Ukraine.