Vyasna, whose founder and Nobel Peace Prize laureate Ales Bialiatsky, identified 93 prisoners of particular concern among the detainees, who were suffering from cancer, heart disease and other conditions.
“In captivity, all diseases progress quickly, and the worst factor is the lack of medical care,” said Vyasna representative Pavel Sabelka.
“It suffers from the conditions of detention – lack of fresh air, poor nutrition, constant psychological pressure and stress,” he added.
Belarus launched a tough crackdown on the opposition after large protests spread across the country following August 2020 elections, whose controversial results installed dictatorial President Alexander Lukashenko for a sixth term.
About 35,000 human rights activists have been detained in the crackdown, many of them beaten by the police.
All major opposition figures were detained or fled the country.
Vyasna says there are currently 1400 political prisoners in jail.
Among the cases cited by Vyasna in the report is Maria Kolesnikova, who was one of the most prominent leaders of the post-election protests.
He underwent abdominal surgery but was soon taken to prison.
Vyasna claims that food requirements were not met and investigation revealed that she was assaulted before being admitted to the hospital.
Other cases identified include 19-year-old Mikita Zaladaro, who reported being denied pills to control epilepsy, and Yevhen Barosky, who told his family when he was sick: “I'm probably going to die here.”