Artur Khomenko, an entrepreneur from Minsk, said police officers began beating him with their fists and truncheons after they detained him on the fourth night of huge protests that have weakened Belarusian leader Alexander Lukashenko's grip on power.
Then they pulled down his underwear and threatened to rape him with a truncheon, before beating him and making him kneel handcuffed on the floor face down for four hours, he said.
Khomenko spent most of the next week in the Emergency Hospital in Minsk with searing head pain and partial hearing loss in one ear. The hospital declined to comment.