Belarus police carried out mass arrests as tens of thousands of people again gathered for protests calling on leader Alexander Lukashenko to step down.
More than 50 people were arrested on Sunday, said rights group.
Video footage showed police spraying an irritant directly into the faces of protesters in one city.
This was the 50th day of protests following August’s disputed presidential vote. Earlier this week Lukashenko held a secret inauguration.
According to the electoral commission, Lukashenko won a sixth term with more than 80% of votes. But the opposition has disputed this, saying he cheated and that they won the election with at least 60% of the vote.
Several EU countries and the US say they do not recognize Lukashenko as the legitimate president of Belarus.
Police have admitted that they used tear gas and stun grenades to disperse what they called “disobedient” protesters in the eastern city of Gomel on Sunday.