Black-clad riot police clubbed demonstrators as government opponents on Saturday marched in defiance of a show of force by Alexander Lukashenko, the president, that has drawn Western sanctions.
Nearly a week into protests set off by a disputed election that handed Lukashenko a third term, opposition leader Alexander Milinkevich told a crowd of thousands before the march on Saturday that momentum is growing to bring democracy to Belarus.
The day of confrontation and wildly swinging emotions left two huge questions for the ex-Soviet republic of 10 million people, characterised in the West as Europe's last dictatorship: How much dissent are the authorities willing to allow and how much support does the opposition have?
Milinkevich was speaking at an impromptu rally held at a Minsk park after police shoved back protesters from the central city square where they had intended to gather.
Police didn't interfere with the park rally that attracted around 7000 people - raising hopes that security forces' long history of violence against dissenters was softening.
But authorities showed their tolerance had distinct limits after rally participants tried to march to a jail where some of the hundreds of people arrested over the past week are being held.
A three-deep phalanx of riot police with shields confronted the marchers at a railroad underpass, then pushed them up the street, beating some bloody with truncheons and arresting about 20.
At least four percussion grenades were detonated; Vladimir Naumov, the interior minister, later denied the explosions were set off by police, but did not say what caused them.
More than 100 were arrested throughout the day, said Ales Byalyatsky of the human-rights group Vasnya. Among those arrested at the confrontation with riot police was Alexander.
The crowd at the park was the biggest since the first night of protests on 19 March, when about 10,000 people turned out, but the large number was counterbalanced by hundreds of others who walked by in apathy, disgust or fear of taking part.
The crowd was mostly people aged up to about 30, with a large minority of elderly. Middle-aged or middle-class people were few, indicating the opposition has little support in a potentially critical sector of society.
Milinkevich nonetheless appeared elated by the turnout. "The people have come out today, they have come out in the face of truncheons, in the face of arrests," he said.
"The more the authorities conduct repression, the closer they bring themselves to their end."
Demonstrators held flowers, waved the red-and-white historic flag of the opposition and shouted "Milinkevich!" and "We are not afraid!"
Milinkevich called for the next rally to take place on 26 April, apparently aiming to end the immediate tensions of daily rallies and to give the opposition time to plot strategy.
The day is the 20th anniversary of the Chernobyl nuclear power-plant explosion; Belarus was in the direct path of the radiation and the anniversary is likely to underline discontent over Lukashenko's moves to repopulate evacuated areas of the contamination zone.
Saturday's confrontation came a day after police stormed a tent camp in Oktyabrskaya Square that had been the focus of around-the-clock protests over the election in which Lukashenko won a new five year-term by a landslide.
The opposition denounced the vote as a farce and the West criticised it as undemocratic.
Milinkevich, who officially received about 6% of the vote and wants a new election without the participation of Lukashenko, had been calling all week for a major demonstration on Saturday marking the anniversary of Belarus' first independence declaration in 1918.
Police did not prevent people from joining his rally at the park. A row of police buses stood nearby.
The European Union and the US said on Friday that they would impose sanctions on Lukashenko, who they say has turned Belarus into Europe's last dictatorship. Both called for an immediate end to the crackdown on the opposition.
Meanwhile, Russia's UN ambassador has said the US and the European Union are taking the wrong action in response to the disputed election in Belarus.
Andrey Denisov, Russia's ambassador to the UN, and Zhang Yishan, China's deputy UN ambassador, delivered remarks at New York's Lehman College on Saturday.
Denisov also said he is averse to looking at issues from a singular perspective, noting that today's global problems require collective approaches.
"Ideological-driven approaches to international relations attempt to impose one's own cultural and social standards on others," Denisov said.