When the captain of Ryanair flight 4978 from Athens to Lithuania's capital Vilnius announced the plane was being diverted to Minsk, capital of neighbouring Belarus, one passenger reacted immediately.

He stood up from his seat, pulled a laptop computer from his hand luggage in the overhead storage and passed it to a female companion, along with his mobile phone.

Belurusian dissident journalist Roman Protasevich, who is wanted in Belarus for his role in broadcasting huge opposition protests in Minsk last year, did not have much time.

Minsk is less than 200 km from Vilnius. The diversion would take minutes.

"When it was announced they were going to land in Minsk, Roman stood up, opened the luggage compartment, took luggage out and was trying to split things," a fellow passenger, who gave his name as Mantis, said.

"I think he made a mistake. There were plenty of people, so he could [have given] the things to me or other passengers and not the girlfriend, who was also I think arrested."

Flying alongside the plane was a Soviet-era MiG-29 jet fighter, with orders from Belarusian President Alexander Lukashenko to force the plane to head to Minsk.

Belarusian authorities had diverted the flight as it passed over the country because of a suspected bomb alert, state news agency BelTA said. The alert later turned out to be false.

Fellow passengers could only watch as Protasevich was led away

Mr Protasevich was immediately separated on arrival in Minsk and checks of luggage using sniffer dogs turned up nothing.

Passengers from the plane described hours spent with no information and seeing Mr Protasevich being led away by security.

"We saw that Roman was stopped due to some things in the luggage," Mantis said, adding that the other passengers also had their luggage checked and were taken by bus to the terminal where they spent several hours waiting to reboard the plane.

"We saw from the window that Roman is standing alone, and one policeman with dog was trying to find something [in his luggage]."

Another passenger, who also did not give his name, told Lithuanian media that Mr Protasevich had identified himself to Belarusian security officials on arrival.

"I saw how his passport was taken away. He took off his mask and said, 'I'm so-and-so and I'm the reason why all this is going on,'" he said.

"It's not normal. You cannot have this power to do this, and I think our government should not accept that and there should be some sanctions on Belarus to have done that," Arthur, a French passenger, said. 

"They can pretend there is a bomb alert, to stop your plane, so for sure it wasn't true. The dogs were more there to cover their excuse, but the facts are, they just wanted to arrest a man."

"I saw this Belarusian guy with girlfriend sitting right behind us. He freaked out when the pilot said the plane is diverted to Minsk. He said there's death penalty awaiting him there," passenger Marius Rutkauskas said.

"We sat for an hour after the landing. Then they started releasing passengers and took those two. We did not see them again," Mr Rutkauskas said.

Another passenger, speaking to reporters without giving her name, said Mr Protasevich looked "super scared".

"I looked directly into his eyes and he was very sad," she said.

Lithuanian President Gitanas Nauseda later told a news conference that Mr Protasevich's female companion had not got back on the flight from Minsk to Vilnius.

Wanted for 'extremism' after political protests

Mr Protasevich 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 Mr Lukashenko.

Mr Protasevich, who now works for a different Telegram channel called Belamova, is wanted in Belarus on extremism charges and stands accused of organising mass riots and of inciting social hatred, allegations he denies.

He had fled the country for Poland, and faces charges that could carry a prison sentence of up to 15 years.

Months of protests began in Belarus last year after a presidential election which returned Mr Lukashenko to office for a sixth term.

The result was widely condemned as rigged.

Police cracked down on the protests harshly, detaining around 30,000 people and beating many of them.

Although protests died down during the winter, Belarus has continued to take action against the opposition and independent news media.

The presidential press service said Mr Lukashenko personally ordered the MiG-29 to accompany the Ryanair plane to the airport in the capital Minsk.

The country's opposition has called it a state-sponsored "hijacking".

The European Union called for Mr Protasevich's immediate release, with the head of the European Commission, and the Polish Prime Minister, describing the incident as a hijacking.

Lithuania's President called the incident a "state-sponsored terror act".

He said the European Council would discuss the case on Monday and that he would propose banning Belarusian planes from European Union airports, along with the impostion of "serious sanctions" against Mr Lukashenko's government.

ABC/wires