Belarus opened a criminal investigation on Wednesday into protests that flared a day earlier against the barring of two main rivals to President Alexander Lukashenko in next month's election.
Police said more than 250 people were arrested during Tuesday's demonstrations, mainly in the capital Minsk but also in other cities.
The Belarusian Investigative Committee announced that it had opened an investigation concerning the "organisation or participation in gross violations of public order," a crime punishable by three years in prison.
Protesters showed their support for Viktor Babaryko, a 56-year-old former banker, who would have been Lukashenko's key challenger in the presidential election on August 9.
Lukashenko, nicknamed "Europe's last dictator", has been Belarus' president for the last 26 years. It will be his sixth term in office if re-elected this year.
Key opponents barred
Babaryko has been detained since June over accusations of embezzlement and fraud, which he denies. The electoral commission rejected his candidacy on the grounds of unreported income and foreign funding for his campaign.
Heavyweight candidate and former ambassador to the United States Valery Tsepkalo was also rejected by the electoral commission last month after signatures on a supporting petition were nullified.
'Excessive' use of force
Human rights group Viasna said at least 32 protesters from Minsk have been released, but some of them have been ordered to appear in court for participating in an unauthorised demonstration. If found guilty, they could face short prison sentences or fines.
"Protesters claim that the sole reason Alyaksandr Lukashenka’s political opponents have been purged from the campaign is so that he can seek a sixth consecutive term as president, effectively unopposed," said Aisha Jung, Amnesty International's Belarus Senior Campaigner.
The NGO said around 220 people were arrested during Tuesday's protests and police sought to disperse "peaceful gatherings" with "excessive and unnecessary use of force".
Speaking on Wednesday, President Lukashenko assured that he would defend Belarus "with all legal methods" and that he would "not give his country to anyone".
He also lambasted European critics.
"Do not point your finger at us telling us how to live. We already know how to live," he said, according to remarks transcribed on the presidency website.
With top opponents Tsepkalo and Babariko barred, the candidates now in the presidential race are:
Alexander Lukashenko: President of Belarus since 1994
Anna Kanopackaja: A lawyer and a former MP
Sergeij Cherechnia: Chairman of Belarus’ Social Democratic Party
Andreij Dmitrijev: Co-chairman of the Speak the Truth movement
Svetlana Tikhanovskaya: Wife of a prominent blogger Sergei Tikhanovsky who was barred from taking part