Belarus opposition leader Svetlana Tikhanovskaya has urged the UN to help halt the authorities' crackdown on protesters.
She said the options should include UN sanctions targeting individuals close to Alexander Lukashenko, who she said was "desperately clinging to power".
On Friday police in Minsk arrested five university students who were in a group singing a protest anthem from Les Miserables.
Mass anti-Lukashenko protests continue.
Videos posted on Twitter showed chaotic scenes at the Minsk State Linguistic Institute on Friday, with police dragging students away through crowded corridors.
Ms Tikhanovskaya, who was forced to go into exile in neighbouring Lithuania, urged the UN via video link to send an international monitoring mission to Belarus immediately to "document the situation on the ground".
"A nation cannot and should not be hostage to one man's thirst for power. Belarusians have woken up, the point of no return is passed," she told the UN informal meeting called by Estonia, one of Lithuania's Baltic neighbours.
Ms Tikhanovskaya was the chief opposition rival to Alexander Lukashenko in the 9 August election - she entered the presidential race after her husband Sergei Tikhanovsky and another candidate were jailed.
She said the opposition was demanding an end to the police violence, the immediate release of all political prisoners and a free and fair election.
"Collaboration with the regime of Lukashenko means support for violence," she told the UN meeting, urging the UN to "use all mechanisms to halt the violence, including sanctions on the individuals that committed electoral violations and crimes against humanity."
"Lukashenko doesn't represent Belarus anymore," she added.
Last month EU leaders agreed to impose sanctions - including asset freezes - on as yet unnamed Belarusian officials involved in alleged election-rigging, brutality and imprisonment of protesters. The exact sanctions are still being worked out.
The UN special rapporteur on Belarus, Anais Marin, told the UN meeting that Mr Lukashenko's re-election as president - after 26 years in power - was "completely manipulated" and "people's votes were stolen".
She accused the Belarus police of torture, citing as one example a 16-year-old who was "so badly beaten up he was left in a coma".
"The authorities must release all those arbitrarily arrested," she said. "The government is waging an insane war against its own people."
In her address, Ms Tikhanovskaya demanded that the authorities grant the rapporteur entry to Belarus and free movement there.