Belarus police detained dozens of people in Minsk on Sunday during the latest in months of anti-government protests since a disputed presidential election in August, human rights activists reported.
Thousands of people took to the streets of Belarusian capital and police used stun grenades to disperse the crowd, several Belarus media outlets reported.
The Vesna-96 rights group said 70 people had been detained so far.
Opponents have staged regular protests since August, accusing President Alexander Lukashenko of rigging the election to extend his 26-year grip on power. He denies electoral fraud and has refused to resign.
Protest organisers this week asked people to gather in dozens of different spots all across Minsk before forming bigger groups, to make it more difficult for police to control the crowd.
The street rallies were reignited following the death of a 31-year old anti-government protester Roman Bondarenko, who died in hospital earlier this month following what demonstrators said was a severe beating by security forces.
The interior ministry denied responsibility for Mr Bondarenko's death, saying he was killed in a scuffle with civilians.