UN human rights chief Navi Pillay on Monday condemned the detention and harassment of political opponents in Belarus as serious violations, after an anti-government protestor was jailed last week.
Pillay expressed concern in a statement at the "harsh sentencing" of Vasily Parfenkov on Thursday and the prospect of "dozens of trials" against imprisoned opposition leaders and supporters.
"The prosecution and sentencing are particularly troubling given that he, together with dozens of other opposition activists, is facing trial for exercising his right to freedom of peaceful assembly and freedom of expression," she said.
"The continued detention of political opponents, harassment of civil society and intimidation of the independent media are serious human rights violations," the UN High Commissioner for Human Rights added, reiterating a call for the release of political detainees.
A court in Minsk convicted Parfenkov on charges of organising mass disturbances during a rally in the former Soviet republic's capital after President Alexander Lukashenko's disputed re-election on December 19.
The UN human rights office said 30 to 40 people were detained following the protests and a subsequent crackdown on opponents, many in a special detention centre of the KGB of Belarus.
"We have also received reports of the continued intimidation of lawyers who provide legal counsel to the detainees and journalists," Pillay noted.
Five former presidential candidates along with 37 other leading opposition activists have been charged after tens of thousands protested the polls, described as neither free nor fair by foreign monitors.
Western countries have expressed outrage at the crackdown.
The next hearing on Tuesday involves two Russian nationals, Ivan Gaponov and Artyom Breus, whose cases have become a sensitive issue in Russia-Belarus relations.