The jailed Belarusian opposition leader Maria Kolesnikova has been taken from prison and placed in intensive care in hospital, her allies say.
They say Ms Kolesnikova, 40, is in a serious but stable condition in the eastern city of Gomel after having surgery on Monday.
She was jailed for 11 years in 2021, after mass protests at the discredited re-election of Belarus' leader Alexander Lukashenko a year before.
She said the charges were trumped up.
"I don't regret anything," she told the BBC's Sarah Rainsford in 2021, "and I'd do the same again."
Ms Kolesnikova's Twitter account, run by her allies, wrote that "Maria was transferred to hospital…and operated on 28 November.
"Now she is in a stable, serious condition with improvement. Tomorrow [30 November] she is to be transferred to the surgical department."
Belarus' opposition groups and jailed opposition politician Viktor Babariko made similar comments. Her lawyer was earlier not allowed to visit her, reports say.
It emerged earlier this month that Ms Kolesnikova had been put in solitary confinement. It's not known why she needed surgery – her team saying on Twitter only that she had a "surgical pathology".
Belarus' prison authorities have not commented.
Mass street protests swept Belarus soon after Mr Lukashenko was declared the winner of the presidential elections in 2020. The opposition says the results were falsified, and the real winner was Svetlana Tikhanovskaya.
Many demonstrators were brutally beaten while some – like Ms Tikhanovskaya – have been forced into exile, as Mr Lukashenko, who has been in power since 1994, tries to crush all dissent.
In 2020, the Belarusian security forces tried to deport Ms Kolesnikova to Ukraine, after kidnapping her in Minsk.
But she refused to leave the country, ripping up her passport at the border and climbing out of the car window.
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