The Belarusian Supreme Court has rejected an appeal lodged by opposition leader Sviatlana Tsikhanouskaya to annul the results of the disputed presidential election held earlier this month, the TASS news agency has reported.
Veteran leader Alexander Lukashenko declared a landslide win in the 9 August vote, sparking mass protests and allegations of election rigging.
Despite most major opposition figures being in jail or in exile, President Lukashenko has so far failed to put down popular protests against his 26-year rule, more than two weeks after the election.
Two opposition leaders have appeared in court after a night in jail, as the government pursues a crackdown on the few figures still at large, with more mass demonstrations planned.
Tens of thousands of people took to the streets over the weekend and dispersed peacefully. Mr Lukashenko has denied election rigging. He has called the protesters "rats" and says they are funded from abroad.
Olga Kovalkova, the main representative still in Belarus of Ms Tikhanovskaya, appeared in an online court hearing, as did Sarhei Dyleuski, who has led strikes at the Minsk Tractor Factory, one of the country's biggest plants.
Both were arrested yesterday and have been sentenced to ten days in jail.

The two are leaders of the opposition Coordination Council, set up last week with the stated aim of opening negotiations with the government.
The council said that Mr Dyleuski was found guilty of disobeying an order made by the authorities, while no details were provided of what Ms Kovalkova had been sentenced for.
She said that a piece of her heart and soul will always in be Ireland and she remembers with gratitude Ireland's help down through the years. @MichealMartinTD
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Mr Lukashenko has called the council an illegal attempt to seize power and prosecutors have launched a criminal case against it.
The council includes dozens of figures representing broad swathes of society, among them author Svetlana Alexievich, winner of the Nobel Prize for Literature, who has been summoned for questioning tomorrow.
Exiled opposition leader Ms Tikhanovskaya told the EU parliament today that a "peaceful revolution" was underway in Belarus.
"A peaceful revolution is taking place," Ms Tikhanovskaya, 37, said via video link from Lithuania, adding that the mass demonstrations were not for or against either Russia or the European Union.
Yesterday, Taoiseach Micheál Martin and Ms Tikhanovskyaya spoke by phone during which Mr Martin expressed solidarity with the opposition movement.
Ms Tikhanovskyaya, who travelled to Ireland on numerous occasions in her youth, said a piece of heart and soul would always be in Ireland.
Later today, teachers in Belarus are scheduled to hold a demonstration. Mr Lukashenko has threatened to fire any teachers who do not support the government.