MOSCOW — Belarusian authorities on Sunday forced a civilian jetliner to land in Minsk and arrested an opposition journalist who was on board, an act that some European leaders were comparing to a hijacking.

The seizure of the flight between Athens and Vilnius, Lithuania — the capitals of two NATO nations — had little recent precedent, and European leaders meeting in Brussels on Monday said they were considering wide-ranging sanctions against Belarus.

Mere minutes before the Ryanair flight was to exit Belarusian airspace and cross into Lithuania, its crew got an order from Belarus's air traffic control to turn around because of possible explosives on board. A MiG-29 fighter jet scrambled to escort the Boeing to Minsk, though the plane's destination of Vilnius was far closer.

The Belarusian opposition said the purported bomb scare was just a pretext for strongman President Alexander Lukashenko's real reason for ordering the plane's diversion: the arrest of Roman Protasevich, an opposition journalist on board.

The act is the latest by Lukashenko to crack down on dissent. Lukashenko, who has been in power since 1994, claimed a sweeping victory in last year's elections — a result internationally denounced as rigged. Months of popular protests over his rule followed, prompting sweeping repressions that has left most of the opposition exiled or jailed.

With his regime already at odds with its Western neighbors over his harsh treatment of protesters, forcing down the Ryanair plane Sunday is likely to trigger a renewed international effort to punish Lukashenko.

Polish Prime Minister Mateusz Morawiecki said he wanted to discuss immediate sanctions at a previously scheduled meeting of European leaders in Brussels on Monday.

"Hijacking of a civilian plane is an unprecedented act of state terrorism. It cannot go unpunished," he wrote on Twitter.

The news service for the airport in Minsk, the Belarusian capital, said that while the flight was diverted because of reports that there were explosives on board, a bomb was not found on the plane, which had 123 passengers. Lukashenko personally ordered the fighter escort, the BelTA state news agency said.

Protasevich, who ran the popular social media Telegram channel Nexta, was detained upon the plane's landing. The flight was headed to Vilnius, Lithuania, where the 26-year-old has been living in exile.

Protasevich faces more than 12 years in prison after he and the creator of Nexta, which exposed Belarusian police brutality during anti-government demonstrations last year, were added to a list of individuals purportedly involved in terrorist activities. Nexta and its sister channel, Nexta Live, have close to 2 million subscribers.

Protasevich said on his Telegram channel earlier Sunday before departing Greece that he sensed he was under surveillance.

"The regime forced the landing (of the) Ryanair plane in Minsk to arrest journalist and activist Roman Protasevich," opposition leader Svetlana Tikhanovskaya said on Twitter, adding that she is demanding his "immediate release" and calling on the International Civil Aviation Organization to take action.

The ICAO said in a statement on Twitter that it is "strongly concerned by the apparent forced landing of a Ryanair flight and its passengers, which could be in contravention of the Chicago Convention. We look forward to more information being officially confirmed by the countries and operators concerned."

The Ryanair flight was nearly at the Lithuanian border before it made a U-turn to divert to Minsk, according to the Flightradar24 website.

Ryanair said in a statement that Belarusian air traffic control notified its crew that there was "a potential security risk on board" and instructed it to divert "to the nearest airport, Minsk." But the plane was much closer to the Vilnius airport than to the one in Minsk, according to the flight tracker.

Nothing untoward was found, the statement said. The flight departed for Vilnius at 7 p.m. local time in Minsk.

"This is unprecedented," said a senior European diplomat, speaking on the condition of anonymity because of the sensitivity of the unfolding situation.

The diplomat said European policymakers would need to discuss whether it was still safe to fly over Belarusian airspace.

Flights in Northern and Eastern Europe often try to avoid Russian airspace — including the exclave of Kaliningrad on the Baltic Sea — which means that if Belarusian airspace is also a no-go, north-south flights in Europe could become quite circuitous.

Protasevich had been in Athens taking photographs during a visit by Tikhanovskaya to Greece, so his whereabouts would have been public to anyone with an interest. The senior diplomat noted that investigative open-source outlets such as Bellingcat have been able to purchase flight manifests and that it would probably not have been difficult for Belarusian authorities to gain access to information about Protasevich's travel plans.

While Belarus's biggest ally, Russia, was silent on the incident, the Western condemnation was strong. Lithuanian President Gitanas Nauseda said on Twitter that the plane was "forcibly landed" and that the Belarusian "regime is behind the abhorrent action."

NATO Secretary General Jens Stoltenberg said "this is a serious (and) dangerous incident which requires international investigation." British Foreign Secretary Dominic Raab said that Britain is "coordinating with our allies. This outlandish action by Lukashenko will have serious implications."

Julie Fisher, the U.S. ambassador to Belarus, said on Twitter that Lukashenko's "regime today showed again its contempt for international community and its citizens."

"Faking a bomb threat and sending MiG-29s to force @Ryanair to Minsk in order to arrest a @nexta journalist on politically motivated charges is dangerous and abhorrent," she added.

Birnbaum reported from Riga, Latvia.

Europe