Ryanair said Belarusian flight controllers told the crew there was a bomb threat against the plane as it was crossing through Belarus airspace on Sunday and ordered it to land. A Belarusian MiG-29 fighter jet was scrambled to escort the plane in a brazen show of force by President Alexander Lukashenko, who has ruled the country with an iron fist for over a quarter-century.

Belarus authorities then arrested passenger Protasevich, a 26-year-old activist, journalist and prominent critic who ran a popular messaging app that played a key role in helping organise massive protests against the authoritarian leader.

Protasevich and his Russian girlfriend were taken off the plane soon after it landed, and authorities have not said where they are being held. Ryanair Flight FR4978, which began in Athens, Greece, was eventually allowed to continue on to Vilnius, Lithuania.

EU leaders were particularly forceful in their condemnation of the arrest and the move against the plane, which was flying between two of the bloc’s member nations and was being operated by an airline based in Ireland, also a member.

The bloc summoned Belarus’ ambassador “to condemn the inadmissible step of the Belarusian authorities” and said the arrest was yet again “another blatant attempt to silence all opposition voices in the country”.

President Gitanas Nauseda of Lithuania urged the EU to take “clear actions to change the pattern of behaviour of this very dangerous regime”, and said a previously planned EU summit on Monday would assess whether to close its airspace to Belarus carriers, declare Belarusian airspace as unsafe and expand sanctions against Lukashenko’s government.

German Chancellor Angela Merkel condemned the “unprecedented action” of the Belarusian authorities and demanded that Protasevich and his girlfriend, Sofia Sapega, be released immediately.

Czech Prime Minister Andrej Babis said “the scandalous incident in Belarus shows signs of state terrorism and it’s unbelievable”, while EU Commission President Ursula von der Leyen said it amounted to a “hijacking”.

EU leaders have tried to encourage democratic reforms in Belarus and reduce the influence of Russia, to no avail. Ahead of their summit, some EU leaders threatened more sanctions – from scrapping landing rights in the bloc for Belarus’ national carrier Belavia to exclusions from sports events.

Without waiting for the EU, Latvia’s airBaltic said it would avoid Belarusian airspace, and Lithuania’s government said it would instruct all flights to and from the Baltic country to avoid Belarus as well, starting on Tuesday.

British Transport Secretary Grant Shapps said he instructed Britain’s Civil Aviation Authority “to request airlines avoid Belarusian airspace to keep passengers safe”. He said he was suspending the permit allowing Belavia to operate in Britain.

Ukraine President Volodymyr Zelensky ordered officials to move to cut the air link with Belarus and ban Ukrainian flights via the neighbour’s airspace.

The US and the EU have imposed sanctions on top Belarusian officials amid months of protests, triggered by Lukashenko’s re-election to a sixth term in August 2020 balloting that the opposition rejected as rigged. More than 34,000 people have been arrested in Belarus since then, with thousands beaten.

The Belarusian Foreign Ministry bristled at what it described as “belligerent” EU statements, insisting Minsk acted “in full conformity with international rules”.

It ordered all Latvian diplomats out of the country after the Belarusian flag was replaced on Monday with the white-and-red one used by the opposition at a hotel where teams in the world ice hockey championship are staying in Riga, Latvia; the event was moved from Minsk amid the international outcry over the crackdown. Latvian Foreign Minister Edgars Rinkevics took part in the flag replacement.

After Belarus ordered the Latvian diplomats to leave, Latvia announced reciprocal expulsions.

Lufthansa said a flight from Minsk to Frankfurt with 51 people aboard was delayed on Monday following a “security warning”. It was allowed to depart after the plane, passengers and cargo were searched.

On Sunday, flight tracker sites indicated the Ryanair flight was about 10 kilometres (6 miles) from the Lithuanian border when it was diverted. There were conflicting reports on what exactly happened.

Belarusian transport ministry official Artem Sikorsky said the Minsk airport had received an email about the bomb threat from the Palestinian militant group Hamas.

Lukashenko’s press service said he had ordered a fighter jet to accompany the plane after being told of the bomb threat. Deputy air force commander Andrei Gurtsevich told Belarusian state TV that the Ryanair crew decided to land in Minsk, adding that the fighter jet was sent “to ensure a safe landing”.

But Ryanair said in a statement that Belarusian air traffic control instructed the plane to divert to the capital. The plane was searched, and no bomb was found.

Ryanair chief executive Michael O’Leary described the move as “a case of state-sponsored hijacking … state-sponsored piracy”.

In an apparent reference to the Belarusian security agency that still goes under its Soviet-era name KGB, O’Leary said he told the Irish radio station Newstalk that he believes “some KGB agents offloaded from the aircraft” in Minsk.

Of the 126 people aboard the flight initially, only 121 made it to Vilnius, according to Rolandas Kiskis, chief of criminal police bureau in the Lithuanian capital where an investigation has begun.

Passengers described Protasevich’s shock when he realised the plane was going to Minsk.

“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 a death penalty awaiting him there,” passenger Marius Rutkauskas said after the plane finally arrived in Vilnius. “We sat for an hour after the landing. Then they started releasing passengers and took those two. We did not see them again.”

Protasevich was a co-founder of the Telegram messaging app’s Nexta channel, which played a prominent role in helping organise the anti-Lukashenko protests.

Nearly 2 million Belarusians in the nation of 9.3 million people have followed the channel, which has been the main conduit for organising demonstrations and offered advice on how to dodge police cordons. It also has run photos, video and other materials documenting the brutal police crackdown on the protests.

Belarus authorities have labelled the channel “extremist” and charged Protasevich in absentia of inciting mass riots and fanning social hatred. He could face 15 years in prison if convicted.

In November, the Belarusian KGB also put Protasevich on the list of people suspected of involvement in terrorism, an ominous sign that he could face even graver charges. Terrorism is punishable by death in Belarus, the only country in Europe that maintains capital punishment.

Amid the international outrage, Moscow quickly offered help to its ally.

Russian Foreign Minister Sergey Lavrov said the episode needs to be investigated – but that it could not be rushed. Moscow and Minsk have close political, economic and military ties, and Lukashenko has relied on Russian support amid Western sanctions.

In a previous diversion of a passenger flight, a United Airlines flight in 2004 from London to Washington carrying the singer Yusuf Islam, better known as Cat Stevens, was sent to Bangor, Maine, where FBI agents met the plane and sent him back to England. US officials said he was denied access to the United States on national security grounds. He later was allowed into the US.