Victor Babariko, the main rival of long-time Belarus president Alexander Lukashenko, has been barred from running in next month's election.
The decision was made by Belarus’ Central Election Commission on Tuesday, a spokesperson for Babariko confirmed to Euronews.
Babariko was detained on June 18 during the reported arrest of several hundred opposition supporters. Charges of embezzlement and fraud have been brought against Babariko, who is currently being held in a KGB detention centre in the capital Minsk.
The commission said the 56-year-old former banker's candidacy had been rejected due to unreported income and foreign funding for his campaign.
Alexandr Feduta, a Belarusian journalist and analyst: "I do not think that something extraordinary happened with the barring of Babariko from the race. Everybody knew that this will happen sooner or later - if not today then during the period of the active electoral campaign. There is always a stick to beat someone."
Marina Kolesnikova, a member of Babariko's election campaign team, said: “We are still waiting for the official document denying the right to our candidate but the accusations that have been brought against him are absolutely preposterous and unsubstantiated.
"Even having been incriminated with the crimes he has never committed, he should have been allowed to run unless court proves his guilt,” she said.
Kolesnikova said they encourage all Belarusians to participate in the election and vote for “any” democratic candidate, not for the incumbent Lukashenko, who is seeking his sixth term.
It comes a fortnight after another heavyweight candidate, Valery Tsepkalo, was excluded from the race.
Belarus is set to hold presidential elections on August 9.
Lukashenko, dubbed Europe's last dictator, has been Belarus' president since 1994.
With key challengers Tsepkalo and Babariko barred, the candidates allowed to take part in the presidential race are:
Alexander Lukashenko: President of Belarus since 1994.
Anna Kanopackaja: A lawyer and a former MP.
Sergeij Cherechnia: Chairman of Belarus’ Social Democratic Party
Andreij Dmitrijev: Co-chairman of the Speak the Truth movement
Svetlana Tikhanovskaya: Wife of a prominent blogger Sergei Tikhanovsky who was barred from taking part