Opposition supporters rallied in Belarus capital Minsk, two weeks after a disputed election gave President Alexander Lukashenko another term in office.
Tens of thousands filled the central square despite a heavy police presence.
The protesters say Mr Lukashenko stole the election and want him to resign.
Many were carrying the opposition’s red and white flags, and chanted “freedom” and anti-government slogans.
Pro-opposition media put the crowd at more than 100,000.
After gathering in the square, some demonstrators moved towards the “Hero City” war memorial and the presidential palace, where they were blocked by a security cordon.
The turnout in Minsk today for the manifestation for democracy looks absolutely massive. The regime effort to scare people away have so far failed. Dare the regime send the army against its people? pic.twitter.com/HNbAOKFDVj
— Carl Bildt (@carlbildt) August 23, 2020
Meanwhile in Lithuania, thousands of people – including President Gitanas Nausėda – formed a human chain from the capital Vilnius to the Belarusian border in solidarity with those protesting in Minsk.
More human chains were planned in the Estonian capital Tallinn and in Prague in the Czech Republic.
This weekend’s rally in Minsk follows the country’s biggest protest in modern history last Sunday, when hundreds of thousands filled the streets.
Mr Lukashenko has vowed to crush unrest and blamed the dissent on unnamed “foreign-backed revolutionaries”.
Recent protests were met with a crackdown in which at least four people were killed. Demonstrators said they had been tortured in prisons.
According to official results, Mr Lukashenko – who has ruled Belarus for 26 years – won more than 80% of the vote in the 9 August election and opposition leader Svetlana Tikhanovskaya 10%.
There were no independent observers and the opposition alleges massive vote rigging.
Ms Tikhanovskaya, who was forced to flee to neighbouring Lithuania the day after the election, vowed to “stand till the end” in the protests.