She was taken to hospital earlier this week but doctors did not share her diagnosis or any other details about the surgery.
Ms Kolesnikova’s Twitter account, run by her opposition colleagues, said she had been hospitalised and undergone surgery on 28 November.
Opposition politician Viktor Babariko made similar comments in a Telegram message, saying she had been transferred to a hospital war in the southeastern city of Gomel.
Her father, Alexander, also said she had been taken to hospital, adding that she looked energetic and cheerful when he last visited her in prison in October.
Ms Kolesnikova, an outspoken critic of Mr Lukashenko, was jailed for her role in mass protests that broke out in Belarus in 2020 following the widely discredited reelection of Mr Lukashenko.
She said the charges against her were trumped up. The opposition said the election results were falsified and that the real winner was Svetlana Tikhanovskaya.
Mr Babariko’s telegram channel said Kolesnikova was set to be moved out of the intensive care unit to a surgery ward on Wednesday.
"Our dear Masha (Maria), we all hope that you are going to be okay!" exiled opposition leader Sviatlana Tsikhanouskaya wrote on Telegram, describing the initial report of her hospitalisation as "awful news".
In the protests against the election result, many protesters were beaten.
Others, like Ms Tikhanovskaya, were forced into exile as the Belarus president waged a brutal crackdown on those opposed to his rule.
Mr Lukashenko, who has been called Europe’s last dictator, has been in power since 1994. His security forces tries to deport Ms Kolesnikova to Ukraine. after kidnapping her in Minsk.
But she refused to leave the country and was famously pictured tearing up her passport at the border and climbing out of the window of the car.