Several other cities across the country saw similar crackdowns on protesters.
Interior Ministry spokeswoman Olga Chemodanova said that police efforts to restore order were continuing overnight, but wouldn't say how many people were detained.
Ales Bilyatsky of the Viasna human rights group told The Associated Press several hundred were detained and hundreds injured in the police crackdown.
“What has happened is awful,” Tsikhanouskaya told reporters Sunday.
An AP journalist was beaten by police and treated at a hospital.
At Minsk' Hospital No. 10, an AP reporter saw a dozen ambulances delivering protesters with fragmentation wounds and cuts from stun grenades and other injuries.
“It was a peaceful protest, we weren't using force,” said 23-year-old protester, Pavel Konoplyanik, who was accompanying his friend who had a plastic grenade fragment stuck in his neck.
“No one will believe in the official results of the vote, they have stolen our victory,” stated Pavel.
Pavel Konoplyanik, whose legs were also cut by fragments of police grenades, said he doesn't want to leave the country but fears that he might have no other choice.
Two prominent opposition challengers were denied places on the ballot, but Tsikhanouskaya, the wife of a jailed opposition blogger, managed to unite opposition groups and draw tens of thousands to her campaign rallies, tapping growing anger over a stagnant economy and fatigue with Lukashenko's autocratic rule.