The election commission in Belarus has released the list of candidates who will contest the presidency in March.
Alexander Milinkevich celebrated his official registration for the contest
They include Alexander Milinkevich, the leading figure opposing pro-Moscow President Alexander Lukashenko, who has been in power for nearly 12 years.
Opinion polls suggest Mr Lukashenko, who has dominated election coverage on state TV, will win a third term.
The United States has described the former Soviet republic as the "last dictatorship in Europe".
The list of four candidates - including Social Democratic Party leader Alexander Kozulin and Liberal Democratic Party leader Sergei Gaidukevich - was announced in a solemn registration ceremony on Friday.
Critics accuse President Lukashenko of running an authoritarian state
It was the first and last time the candidates would meet during the campaign, as there will be no joint debates.
Candidates will be restricted to two half-hour pre-recorded speeches each on national television.
Appearing on television for even 30 minutes is a huge success for the three opposition candidates, says the BBC's Kyril Sukhotski in Minsk, as monitoring data over the past two weeks shows that they received considerably less television coverage than Mr Lukashenko.
Since coming to power in 1994, Mr Lukashenko has increasingly been accused by opponents of running an authoritarian state.
The US and the European Union have accused him of cracking down on rival and silencing the media.
The opposition has been campaigning on a platform promoting the ideas of freedom, justice and truth.
On Thursday, dozens of protesters were arrested during anti-government protests in the Belarus capital, Minsk.
The demonstrations, involving about 200 people, were held to remember opposition figures who have disappeared or been imprisoned during Mr Lukashenko's rule.