The dissident Belarusian journalist who was arrested when his plane was diverted to Minsk was brought to a Foreign Ministry news conference on Monday.
The opposition said the appearance by Raman Pratasevich showed he is a hostage.
Mr Pratasevich founded a messaging app channel that was widely used in last year’s massive protests against hardline President Alexander Lukashenko.
He was seized on May 23 when his flight from Greece to Lithuania was diverted to Minsk, accompanied by a Belarusian fighter jet, because of an alleged bomb threat.
Western countries denounced the incident as air piracy by Belarus.
Mr Pratasevich, who faces a potential 15 years in prison, has been shown on state television expressing regret for his activities.
“No matter what he says, let’s not forget: he is a hostage. And the regime is using him as a trophy,” Franak Viacorka, an adviser to exiled opposition leader Sviatlana Tsikhanouskaya, said on Twitter on Monday.
BBC correspondent Jonah Fisher left the news conference when Mr Pratasevich appeared, saying later on Twitter: “Not taking part when he is clearly there under duress.”