There were reportedly fewer people than at previous rallies, which peaked on election night with at least 10,000 demonstrators.
Milinkevich called upon activists to hold a vigil on the square until March 25.
A few dozens supporters had remained on the square all day long, following a night of peaceful protest, listening to music and trying to stay warm amid biting cold.
One woman told reporters she felt exhausted after spending the night on the square.
"We’re waiting for at least a few people to show up. I’d really like to have at least a couple of hours’ sleep because it’s really hard to stay on one’s feet for more than 12 hours."
Police remained on the vicinity of the square all day and reinforcements were sent in as more opposition supporters began gathering toward the evening.
An RFE/RL’s Belarus Service correspondent says authorities turned off electricity on the square, leaving protesters in darkness and without music. Yet, he reports the atmosphere on the square remain cheerful.
Hours earlier, a number of European Union ambassadors could be spotted on the square, chatting with the demonstrators. Belarus's Belapan independent news agency said they included envoys from Britain, France, Germany, the Czech Republic, Slovakia, and Latvia.
"We ambassadors are here because we believe in human rights and the democratic process," British Ambassador Brian Beckett told reporters while on the square. "This is part of the democratic process -- the right of people to express their views, which is very constrained in Belarus. It is very difficult for people to have a debate, to be able to say what they think and even to be able to vote. And so we are here to show that we are aware of that, and we are here to show that we support people of Belarus."
Beatings And Disappearances In The Night
Milinkevich today charged that police had made more than 100 arrests during the previous night. He also accused security forces of resorting to unfair tactics.
"Those cowards are afraid to come here [on the square] to arrest us, although they have no right to arrest us,” Milinkevich said. “Therefore, they’re trying to lure people [out of the square] and twist their arms around the corner. Then they bring charges against them."
A woman whose son disappeared overnight after he tried to reach Kastrychnitskaya Square told RFE/RL’s Belarus Service her other son was beaten up by police.
"A police officer -- a strong one - hit my son on the nose,” she said. “My son looked awful. His nose bled all night. But we cannot find our other son. At six o’clock in the morning, we went to the Akrestsyna detention center. We also called everywhere, but no one is telling us anything."
Among those who were detained yesterday is Anatol Lyabedzka, the chairman of the opposition United Civic Party and a close aide to Milinkevich.
A Minsk court today sentenced Lyabedzka to a 15-day administrative jail sentence on charges of participating in an unsanctioned rally.
After the sentence was read, Lyabedzka addressed reporters outside the courtroom.
"This is the trial of truth and justice. So long as we will have this regime, we will continue to have such trials. Shame on such courts, shame on such judges."
Jail Sentences Handed Out
Belapan quotes rights campaigner Valyantsin Stefanovich as saying a number of opposition supporters received various jail sentences today. Among them is Tatsyana Khoma, a student who was recently expelled from university after attending a youth forum abroad. Khoma received a 10-day jail sentence.
The Belarusian KGB has also detained a Polish lawmaker on charges identical to that brought against Lyabedzka. In Warsaw today, Foreign Ministry spokesman Pawel Dobrowolski identified the lawmaker as Jaroslaw Jagiello, a member of Poland’s Law and Justice ruling party.
Georgia today confirmed that three of its nationals had also been detained overnight. Those include dissident Orthodox priest Basil Kobakhidze, Malkhaz Songulashvili -- the leader of Georgia’s small Baptist community -- and religious freedom campaigner Lado Gogiashvili.
Georgian Deputy Foreign Minister Merab Antadze told a news briefing the three men had been detained "only because they were waving Georgian flags and carrying Georgian passports."
"We call on [Belarusian authorities] to stop such actions against Georgian citizens and release them at once," Antadze said.
Belarus's President Alyaksandar Lukashenka, who won a disputed landslide re-election on March 19, has long accused Georgia of plotting to overthrow his government.
In a mid-morning phone interview with Georgia’s Rustavi-2 private television, Kobakhidze said he and his two companions were still in custody. The three men’s whereabouts remain unknown.
The October Square demonstration on the morning of March 21 (RFE/RL)
MAKING A DIFFERENCE? Some 200 demonstrators remain in central Minsk following an overnight vigil on March 20-21 to protest official election results giving President Alyaksandr Lukashenka a third term in office. Opposition supporters braved the threat of police action to stage a second night of protests in the capital's October (Kastrychnitskaya) Square following the March 19 vote. Russia approved the election, but both the European Union and the United States said the ballot was neither free nor fair. The opposition is calling for a new vote. But it is uncertain what impact, if any, the public protest will have....(more)