Opposition leader Alyaksandr Milinkevich said he will defy the warning from prosecutors and he will lead the rally on October Square, the site of protests last month against the reelection of President Alyaksandr Lukashenka.
Authorities in Minsk gave permission for a rally but warned demonstrators to stay away from October Square, which is in the center of the city.
The opposition has traditionally gathered on the anniversary of the Chornobyl disaster, the world's worst nuclear accident, to protest against Lukashenka's handling of the consequences of the catastrophe.
Busloads of police entered streets near the square hours before the rally was due to start, and police vans line parts of central Minsk.
Alyaksandr Milinkevich attending an opposition rock concert on March18 in Minsk, where he first issued a call for protests (RFE/RL)
TOWARD A SHOWDOWN?: The main Belarusian opposition presidential candidate, Alyaksandr Milinkevich, and his campaign manager, Syarhey Kalyakin, spoke on March 19 at a news conference in Minsk. RFE/RL's Belarus Service provided excerpts from Milinkevich's remarks.
Milinkevich: I believe this civil confrontation can be resolved by repeating elections, in which representatives of all candidates will be represented in election commissions.
Milinkevich: This will not be a true result. It will be a result of falsifications that have been continuing for a long time. [The results] will be recognized neither by us nor the majority of the Belarusian population. They will not be recognized by democratic countries, it has already become obvious.
Milinkevich: I will be appealing to the good senses of the authorities. This conflict should not be escalated. It should not be fomented. A resolution should be found. Let's sit down to the negotiating table.
Milinkevich: I am absolutely confident that democratic countries will not recognize this election as legitimate. I very much hope that there will be quite a few serious politicians in Russia who will do the same.
Milinkevich: Those people who will overcome fear will come out in the streets. There was and still is fear being infused today by warnings of alleged terrorism, which has never been heard of in Belarus. So let's see how many people will come out. I will be grateful to everyone who comes out and says peacefully that we want to live like humans and not on our knees, in humiliation.