Belarusian police arrested five university students in the capital Minsk on Friday, human rights activists said, and videos posted on social media showed chaotic scenes of those detained being dragged away by officers through crowded corridors.

The arrests took place in the building of Minsk State Linguistic Institute, which had warned students several days ago that it would call in the police unless they halted their protests against last month’s disputed re-election of President Alexander Lukashenko.

Social media footage showed several dozen students belting out a chorus of “Do you hear the people sing”, a rousing protest anthem from the musical “Les Miserables”, standing behind the white and red flag that is the emblem of the opposition.

Other clips showed students remonstrating with the police as those arrested were pulled away, and pleading with a university official to respond to the incident.

An interior ministry spokeswoman said the arrests were part of an “administrative process” and were not connected with events on Friday, presumably a reference to the singing.

The five students were released from police custody later on Friday after being charged with taking part in illegal protests, according to social media posts and Belarusian media outlets.

Thousands of students took part in protests across the country on Sept. 1, the first day of the academic year, as part of a wave of opposition to Lukashenko’s Aug. 9 election victory, which his critics say was rigged.

Separately, a court in Minsk jailed six journalists who were detained at the Sept. 1 student protest for three days each, the Belarusian Association of Journalists said. They were found guilty of taking part in illegal protests.

The protests and strikes have confronted Lukashenko with the gravest threat yet to his 26-year-old grip on power in the former Soviet republic.

Broadcaster Euroradio showed video of students confronting university officials after the arrests with chants of “Shame!”

Dozens of people gathered outside the university in a show of solidarity with the students.

Reuters