"We demand that the Belarusian authorities immediately release Roman Protasevich, as well as other illegally detained Polish and Belarusian activists, including Andzelika Borys and Andrzej Poczobut," Mateusz Morawiecki told PAP on Sunday.
"We demand that repressions against independent media and society end immediately," the prime minister said.
Morawiecki made the statement after Belarus forced a Lithuania-bound flight carrying a key opposition activist to land in Minsk on Sunday.
Raman Pratasevich was arrested at the airport. He is a co-founder of the Telegram messaging app's Nexta channel, which Belarus last year declared as extremist after it was used to help organise major protests against Lukashenko.
"The hijacking of a passenger plane and forcing it to land in Minsk with the use of the Belarusian air force is an unprecedented act of state terrorism. It cannot be described in a different way," Morawiecki said.
The prime minister compared the incident to a similar attack by Soviet military jets against a Korean airliner shot down in 1983. "Today, there were no such tragic consequences, but it is clear that the Lukashenko regime is crossing boundaries," Morawiecki said, adding that journalists of the tut.by portal were brutally attacked last week while Bielsat independent television was being constantly harassed.
Morawiecki said that the arrest of Protasevich aroused much concern, especially in view of the death of another opponent of the Lukashenko regime in prison last week.
"Immediately after we were informed about the incident, I asked the foreign minister to launch firm steps regarding this case. The Belarusian ambassador was summoned to the Foreign Ministry," the prime minister went on to say.
Morawiecki also said that the European Union must make an immediate response. "That is why I have asked the European Council's president, Charles Michel, to expand the programme of tomorrow's summit to include immediate sanctions against Belarus."
"The sanctions should, above all, concern air traffic over Belarus and a ban of flights by Belarusian airlines. All persons directly responsible for terrorist actions should face consequences," Morawiecki concluded. (PAP)