Roman Protasevich appears to have a black mark on his forehead in the video, in which he confesses to being involved in organising protests in Belarus in 2020.
European Union leaders have agreed on new sanctions against Belarus in response to the arrest of Belarusian dissident Roman Protasevich, hours after a video of the detained journalist in a detention facility appeared on state television.
The EU sanctions include a ban on the use of the 27-nation bloc's airspace and airports, as well as individual sanctions of officials linked to the forced diversion of a passenger jet flying between two EU countries in order to arrest the opposition blogger.
The EU leaders also called on the International Civil Aviation Organisation to investigate the unprecedented move, which EU leaders have called a "hijacking" and "state terrorism".
The sanctions came after a video of Mr. Protasevich was shown on Belarusian state television on Monday evening (local time).
In the brief clip, Mr. Protasevich said he was in good health and acknowledged having played a role in organising mass disturbances in Minsk last year.
Sitting at a table with his hands folded in front of him and speaking rapidly, Mr. Protasevich said he was in satisfactory health and said his treatment in custody was "maximally correct and according to law." He added that he was giving evidence to investigators about organising mass disturbances.
He says he is in a pre-trial detention facility in Minsk and denies having heart problems reported by some social media.
He also appears to have a small black spot on his forehead.
The comments were immediately dismissed by his allies as made under duress.
"This is how Raman looks under physical and moral pressure. I demand the immediate release of Raman and all political prisoners," a leader of Belarusian opposition, Sviatlana Thiskanouskaya, wrote on Twitter in English, using the Belarusian spelling of his name.
Belarusian President Alexander Lukashenko, 66, has faced the biggest challenge of his nearly 27-year-old rule from protesters who took to the streets after he was declared the winner of an election last year they said was rigged.
About 35,000 people have been detained since the start of regular demonstrations in August 2020. Mr. Lukashenko denies electoral fraud and has accused the West of sponsoring the protests.