The Organization for Security and Cooperation in Europe (OSCE) is voicing strong concern over the start of legal action against opposition protesters in Belarus.
In a statement, OSCE Chairman-in-Office Audronius Azubalis said, "I would like to stress that freedom of assembly is a fundamental democratic right."
He added: "Of particular concern is that parts of the first trial were held in camera. This is unacceptable. I am also concerned about reports of a number of defense lawyers having their licenses revoked."
On February 17, Vasil Parfyankou, 27, was the first to be tried of about 30 protesters detained after a police crackdown on a December 19 rally in Minsk and who include four opposition presidential candidates.
He was sentenced to four years in prison.
The United States has criticized the trials as a further "negative step" by Belarus.
The Belarus Helsinki Committee said the sentence against Parfyankou was clearly politically motivated.