Tens of thousands of demonstrators organised at least 100 separate gatherings in the capital Minsk.
Protesters in Belarus again took to the streets to demand the resignation of President Alexander Lukashenko, who is facing down months of historic protests against his rule.
The Viasna rights group said dozens of people were detained in Minsk on Sunday as authorities deployed water cannon and large numbers of law enforcement blocked off areas of the city centre.
Demonstrators waving the opposition's red and white flag marched on the outskirts of the capital to thwart a large-scale police crackdown.
The opposition-leaning news site Nasha Niva said protesters had organised at least 100 separate gatherings in Minsk and its suburbs.
An AFP correspondent said that unlike previous weekend protests that spurred tens of thousands into the city centre, metro stations were open Sunday and mobile internet was working without interruptions.
Disputed presidential election
Ex-Soviet Belarus has been gripped by historic anti-government demonstrations that erupted after August presidential elections in which Lukashenko claimed a sixth term in office.
His opponents claim the polls were rigged and that political novice Svetlana Tikhanovskaya, who ran in place of her jailed husband was the true winner.
Tikhanovskaya, who is in exile in neighbouring Lithuania, hailed protesters who had gathered "despite repressions, violence and cold.
"They resist Lukashenko's regime because the people of Belarus want to live in a democratic and free country," she wrote on Twitter.
The European Union imposed sanctions on Lukashenko and his allies citing election rigging and a violent police crackdown on protesters.
On Thursday, Belarus said it will temporarily close its land border in late December to curb the spread of the coronavirus, a move seen by the opposition as a further clampdown on dissent.