Detained journalist Roman Protasevich appeared on Belarusian state TV on Thursday, tearfully confessing to his role in anti-government protests in an interview that the opposition said was made under duress.
In his third appearance since his Ryanair flight was forced to land in Belarus by the authorities on May 23, Protasevich admitted plotting to topple President Alexander Lukashenko by organising "riots" and took back earlier criticism of the veteran leader.
"It's painful to see 'confessions' of Raman Pratasevich," Franak Viacorka, a senior adviser to exiled opposition figure Sviatlana Tsikhanouskaya, tweeted on Thursday.
"His parents believe he was tortured. This is not Raman I know."
Mr Viacorka said Protasevich was "the hostage of the regime and we must make all possible to release him and the other 460 political prisoners".
The opposition said a video confession made last month by Russian citizen Sofia Sapega, Protasevich's girlfriend who was also detained after the forced landing, appeared to be coerced.
Authorities have called Protasevich is an extremist who has enabled violence.
They have insisted that broadcast TV confessions by members of the opposition were made voluntarily.
Protasevich said he was giving the interview, which ran for 90 minutes, of his own volition.
"I'm almost certain they will condemn me publicly and rallies in support of me will come to naught,"Protasevich said of his former associates.
"But I don't care what they will be saying. I immediately admitted my guilt in organising massive unauthorised actions.
"I criticised Alexander Grigoryevich a lot, but when I became more involved in political topics, I began to understand that he was doing the right thing and I certainly respect him."
Western countries and international rights groups have condemned Mr Lukashenko over the forced landing of the aircraft.
They also imposed sanctions against Belarusian officials over a crackdown on protests following a contested election last year.
Ms Tsikhanouskaya said on Monday that she believed Protasevich had been beaten and tortured in prison.
A lawyer who visited him said he was fine.