When young people cross October Square, where opposition groups are hoping to stage the rally, police workers frequently ask for their identification and stop to search their bags.
A number of university students have also discovered their schools have decided to schedule mandatory exams at the same time the rally is scheduled.
"I'm shocked. I was told [by a college official] that I have to take an exam on Sunday at 2 p.m," Nasta Aleksandrovich, a student at a state college in Minsk, told RFE/RL's Belarus Service.
"I asked for an explanation. I was told that Sunday is a working day. And I was told that if I am seen at the rally, I'll be expelled from the college on Monday without many formalities."
The planned demonstration marks what the Belarusian opposition movement calls Freedom Day, the anniversary of the 1918 declaration of the first independent Belarusian state.
It was a short-lived independence. Just 10 months later, Belarus was incorporated into what later became known as the Soviet Union.
The rally also comes just over a year after the country's authoritarian president, Alyaksandr Lukashenka, won an unprecedented third term in a widely criticized election.
Thousands of people convened in central Minsk following the election to protest the results. Hundreds were jailed in the violent police crackdown that ensued.
The government has denied the opposition's current request to hold their rally on October Square. Authorities instead granted permission for the demonstration at a park on the outskirts of Minsk. Opposition activists have indicated that they do not intend to obey the restriction.
"We consistently view the March 25 holiday as an opportunity to display -- in a nonconfrontational way -- the intention of a large part of the Belarusian people to come out in support of the independence of our country and vitally important democratic changes," the organizing committee said in a statement.
"The authorities still have the opportunity to show their goodwill" and allow the rally to be held unchallenged, the statement added.
After falling out with Russia earlier this year over energy prices, Belarusian President Alyaksandr Lukashenka suggested he was ready to forge closer ties with the European Union.
Both the EU and the United States imposed sanctions against Belarus following the March 19, 2006, presidential election amid allegations of voter fraud and human rights violations.
Opposition leaders are using Lukashenka's perceived vulnerability to push ahead with their cause.
"We hope the authorities will understand that in view of the difficult foreign policy situation since the New Year, the time has come to seek understanding, preserve our independence, and save our homeland from division," Reuters quoted former opposition presidential candidate Alyaksandr Milinkevich as saying on March 21.
Milinkevich said delegations from the European Parliament and from the German and Polish legislatures were expected to attend the March 25 rally.
Hans-Gert Pottering, chairman of the European Parliament, said that how Belarusian authorities respond to the demonstration "will become an important test for Lukashenka's regime and demonstrate to Europe the real meaning of his words concerning a closer relationship."
Nevertheless, as the rally approached, authorities continued to round up opposition figures.
On March 21, a Minsk district court sentenced Barys Haretski of the Youth Front opposition group to 12 days in jail on obscenity charges. The same day, a court in Pinsk sentenced Belarusian Popular Front activist Alyaksandr Ramanovich to five days in jail on similar charges.
In early March, Belarusian officials toughened penalties for minor offenses. Most notably, the maximum arrest term for an offense punishable by law was increased from 15 to 25 days.
Many activists and legal experts saw the move as an attempt to ensure that members of the opposition could be in detention at the time of the rally.
In an apparent attempt to draw young people away from the rally, authorities in Minsk have also announced that an open-air concert will be staged the same day.
Minsk, March 25
THE AUTHORITIES GET TOUGH: RFE/RL's Belarus Service filed these images from the police action against the March 25 demonstration in Minsk. Photographs by Maks Kapran.
THE COMPLETE PICTURE: Click on the image to view a dedicated page with news, analysis, and background information about the Belarusian presidential ballot.