Thousands of people took to the streets of Belarusian capital and police used stun grenades to disperse the crowd, several Belarus media outlets reported.
An unregistered Belarusian human rights center, Viasna, said at least 116 people had been arrested across the country on Sunday, majority in Minsk.
Viasna said at least 304 people were arrested throughout the country.
Mass protests gripped Belarus since official results from the August 9 presidential election gave President Alexander Lukashenko a landslide victory over his widely popular opponent Sviatlana Tsikhanouskaya.
Protest organisers this week asked people to gather in dozens of different spots all across Minsk before forming bigger groups, to make it more hard for police to control the crowd.
Security forces deployed heavily around the city with armoured vehicles and water cannons before the rally.
Authorities also restricted mobile internet services and blocked several metro stations to prevent mass gatherings.
Sunday's protests were called a "March Against Fascism" after Lukashenko accused protesters of being fascists.
"I feel like vomiting when I think of the people in power in the country and of the values they are defending".
Belarusian police confirmed to Sputnik they had to resort to riot control tactics to arrest people involved in unauthorized protests in the capital of Minsk on Sunday.
"They want to drag our dignity into the mud", 72-year-old protester Alexandre Ignatov told AFP.
"It's for my dignity, for the future of my children that I have turned out to demonstrate", he added.
The opposition and some poll workers claim the results were manipulated.