The EU has decided to ban Belarusian airlines from European skies after a flight was diverted to Minsk on Sunday and a dissident journalist arrested.
At a meeting in Brussels, the leaders of the 27 member states also told EU airlines not to fly over Belarus, and promised further economic sanctions.
Roman Protasevich, 26, was on a flight from Greece to Lithuania which was rerouted over a supposed bomb threat.
Western countries accused Belarus of "hijacking" the Ryanair plane.
A video has now emerged of Mr Protasevich that appears to have been recorded under duress since his detention at Minsk airport.
In the clip, which was released late on Monday, the journalist said he was in good health and seemingly confessed to crimes he had been charged with by the Belarusian state.
But activists, including the country's main opposition leader, criticised the video and suggested Mr Protasevich was under pressure to admit wrongdoing.
US President Joe Biden described the actions of the Belarusian authorities as "outrageous", saying they were "shameful assaults on both political dissent and the freedom of the press".
Mr Protasevich's father has told the BBC he fears his son may be tortured.
Dmitri Protasevich said on Monday he was "really afraid" of how his son would be treated by the authorities in his home country.
"We hope that he will cope. We are afraid to even think about it, but it's possible he could be beaten and tortured. We are really afraid of that," he said in a video call.
"We are really shocked and really upset," he said. "This sort of thing shouldn't be happening in the 21st Century at the heart of Europe.
"We hope that the whole international community, including the European Union, will put unprecedented pressure on the authorities. We hope the pressure will work and the authorities will realise they've made a really big mistake."
In a separate development on Monday, Belarus expelled the Latvian ambassador and other diplomats after the Belarus national flag was replaced by a historical red-and-white flag used by the opposition at the Ice Hockey World Championships in the Latvian capital Riga.
Latvia responded by expelling Belarus diplomats.