Alexander Kozulin, 50, the leader of the Social Democratic Party, was arrested during a protest March 25 against the results of the March 19 presidential elections that saw President Alexander Lukashenko re-elected to a third term. Kozulin was tried in July.
The press service said the politician, convicted on charges of hooliganism, violating public order and refusing to obey law enforcement officers, would be sent from a pre-trial detention center to a penal colony in the Vitebsk Region in the north of the republic.
The source said Kozulin had taken the news calmly and said he had expected that he would be sent to a colony because he was "aware of the Belarusian leadership's personal attitude" toward him.
Lukashenko, whom Washington had dubbed "Europe's last dictator," was re-elected to a third term with a massive 83% of the vote. Although he has support in his homeland for maintaining relative stability in comparison with some other former Soviet republics, his human rights record has been fiercely criticized by international organizations.
The March elections were denounced by the opposition and international monitors as fraudulent, and opposition activists staged a five-day sit-in in Minsk's central Oktyabrskaya Square.
The March 25 demonstration was broken up by police, and opposition representatives say at least one person died as a result.