Exiled Belarus opposition leader Sviatlana Tsikhanouskaya has said the arrest of a dissident journalist after a Ryanair plane was diverted to Minsk was a panicked miscalculation by the country's authoritarian president Alexander Lukashenko.

She said in an interview: "It was really a mistake. The regime never crossed this red line before, of interfering in a European area.

"This hijacking touched all the European leaders because their citizens were on this flight."

The European Union, the UK, US and Canada united on Monday to impose sanctions on several Belarus officials and organisations in response to the May 23 diversion of Ryanair flight, which was traveling from Greece to Lithuania but was forced to land in Minsk.

Dissident journalist Roman Protasevich was removed from the flight and arrested.

European officials, who likened the diversion to air piracy, also banned Belarus airlines from EU skies and airports.

Mr Lukashenko won a sixth term as president in an election last August which the EU refuses to recognise as legitimate.

The disputed election led to months of mass demonstrations in Belarus, including some that drew as many as 200,000 people.

Authorities launched a brutal crackdown on protesters, and human rights officials say tens of thousands have been detained, with many beaten by security forces.

Lithuanian foreign minister Gabrielius Landsbergis said EU countries thought for months that it still might be possible to reason with Mr Lukashenko - until the Ryanair flight diversion.

"The mood is different now," Mr Landsbergis said.

Ms Tsikhanouskaya was a candidate in the election, running in place of her husband, Siarhei Tsikhanouski, a popular opposition figure who had hoped to stand against Mr Lukashenko but was arrested in May 2020.

A day after the vote, Ms Tsikhanouskaya was forced to flee the country to neighbouring Lithuania, where the 38-year-old political novice lives in exile with her children and has worked to rally European countries against Mr Lukashenko.

"The regime is so frightened by the unity of Belarusians, by the unity of the European Union, the USA, about this situation in Belarus, that they stopped thinking strategically. They started to think emotionally," Ms Tsikhanouskaya told the Associated Press.

On Thursday, her husband's trial is scheduled to begin in the city of Homel on charges of violating public order, inciting hatred and plotting mass disturbances - accusations he rejects. He faces up to 15 years in prison.

"The trial will be closed. The trial will be not in the court, it will be right in the prison. Lawyers will not have an opportunity to tell us what is going on," Ms Tsikhanouskaya said.

She expects the trial to last a month or two, and is not optimistic about the outcome.

"We understand that the trial will not be lawful, will not be honest, will not be fair. In reality, judges can write any number of years in prison," she said.

For Ms Tsikhanouskaya, it is yet another test of her ability as an accidental politician to avoid putting her own feelings for her husband above those of the many Belarusians who have been jailed for opposing the government.

"He's my beloved. I'm thinking about him most of all, because I'm talking about him with my children. I have every day to explain to them where their Daddy is, how he is feeling," she said.

"I assure them that he will come back soon."

She must "separate all those feelings from political duties, because your political duty is to release all of them", Ms Tsikhanouskaya said.

"This is your personal pain. You can cry into your pillow in the evening. But just imagine in what conditions those people are in, what conditions my husband is (in) - without light, without information, without the normal conditions of life. Of course, it's awful," she said.

"But again, it gives me strength not to stop, not to think about myself."

Since he was removed from the Ryanair flight in Minsk, Mr Protasevich has been paraded on state TV, tearfully apologising for his actions and praising Mr Lukashenko.

His parents, members of the opposition and others in the west believe he spoke under duress, with some saying there were signs he had been beaten - a warning that no regime opponent can ignore.

Mr Protasevich's friends say the 26-year-old journalist, who left his homeland in 2019, believed he was being spied upon by Belarusian authorities before his May 23 arrest.

This probably is true for many other political activists from Belarus, said Ms Tsikhanouskaya, who a week earlier had flown with Ryanair from Greece to Lithuania, just like Mr Protasevich.

As she travels Europe to raise awareness about Belarus, she said she feels "more or less" safe.

"People on the ground (in Belarus), they don't have this protection of laws that the European Union has," she said.

Beyond the immediate fate of Mr Protasevich, her husband and others like them, Ms Tsikhanouskaya said difficult times lie ahead for her country.

"This crisis is deepening," she said.

If the authorities in Minsk really cared about people "they would start dialogue with Belarusians, they would release political prisoners, and solve this crisis in a civilized way," she added.

"I imagine new elections this autumn. This is our aim."