Protasevich is the co-founder of social media news channel Nexta, which played a major role in mass protests in Belarus last summer demanding the resignation of President Alexander Lukashenko after his victory in the august 9 elections.
On Sunday, Belarusian flight controllers ordered a Ryanair jetliner flying over the country to land because of a bomb threat and a Belarusian fighter jet was scrambled to escort the plane to Minsk, just before it was to land in Vilnius, Lithuania, from Athens, Greece.
Lukashenko has been in power since 1994 and took his sixth consecutive term a year ago after an election period marred by a brutal crackdown on mass protests against the leader.
They have crossed many red lines and have abandoned common sense and human morals.
European leaders have described Protasevich's arrest as a state-sponsored hijacking and kidnapping, and on Monday called on airlines not to fly over Belarus, while barring Belarusian airlines from EU airspace and airports.
A defiant President Alexander Lukashenko has defended Belarus's diversion of a European flight and arrest of a dissident on board, lashing out at critics at home and overseas. The plane was searched once on the ground, and no bomb was found - but Raman Pratasevich, a 26-year-old journalist and activist, and his Russian girlfriend were detained.
A video released Tuesday showed Sofia Sapega appearing to confess to editing a Telegram channel.
"I continue to cooperate with the investigation and have confessed to organizing mass riots in the city of Minsk", he also said.
"Please, world, stand up and help, I beg you so much because they will kill him, they will kill him".
Ivan Tertel, the chief of the Belarusian state security agency that still goes under its Soviet-era acronym KGB, said that Pratasevich told investigators about "the sponsors of subversive activities against Belarus, its mechanisms and special services and politicians behind it" and promised to release details soon.
"I'm asking, I'm begging, I'm calling on the whole worldwide community to save him", Natalia Protasevich said, weeping.
Foreign Minister Vladimir Makei also said Belarus could opt out of the EU's Eastern Partnership in view of the new sanctions.
Tens of thousands took to the streets to demand the resignation of 66-year-old Lukashenko, who has ruled over Belarus for over two decades.
Diplomatic sources told AFP the UN Security Council would hold an informal meeting on Belarus on Wednesday but was unlikely to agree on a collective statement because of Russia's support for Minsk.