BRUSSELS (AP) — Angry European Union leaders were set to consider a joint response Monday to Belarus' diversion of a plane traveling between EU member nations in order to arrest a prominent Belarusian opposition journalist.

Raman Pratasevich, who ran a popular messaging app that played a key role in helping organize massive protests against Belarus' authoritarian president, was on board the Ryanair flight from Athens, Greece, to Vilnius, Lithuania, when it was diverted to the Belarusian capital, Minsk while flying over Belarus. Belarusian flight controllers had warned the plane crew of an alleged bomb threat and ordered it to land in Minsk, and a Belarusian fighter jet was scrambled to escort the Ryanair airliner.

Shortly after the landing, the 26-year-old Pratasevich and his Russian girlfriend were led out of the plane. The jet was eventually allowed to continue its flight and landed in Vilnius hours behind schedule.

Lithuanian President Gitanas Nauseda on Sunday called the incident a “state-sponsored terror act” and proposed banning Belarusian planes from European Union airports and “serious sanctions” against the Belarusian government.

The 27 EU leaders open a two-day summit later Monday and the issue immediately shot to the top the agenda amid united condemnation of Belarusian President Alexander Lukashenko.

EU foreign policy chief Josep Borrell called it “yet another blatant attempt by the Belarusian authorities to silence all opposition voices.” He called the diversion of the plane an “inadmissible step” highlighting a further worsening in relations between both sides.

U.S. Secretary of State Antony Blinken called the incident “shocking” and accused the Belarusian government of endangering the lives of those aboard the aircraft, including some Americans. He called for the release of Pratasevich and for the Council of the International Civil Aviation Organization to review the incident.

Flight tracker sites indicated the plane was about 10 kilometers (six miles) from the Lithuanian border when it was diverted.

“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 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.”

Pratasevich was a co-founder of the Telegram messaging app’s Nexta channel, which played a prominent role in helping organize major protests against Belarus' President Alexander Lukashenko. The Belarusian authorities have designated it as extremist and leveled charges of inciting riots against Pratasevich, who could face 15 years in prison if convicted.

Months of protests in Belarus were fueled by Lukashenko's election to a sixth presidential term in an August vote that the opposition denounced as rigged. More than 34,000 people have been arrested in Belarus since August, and thousands were brutally beaten.

Dapkus reported from Vilnius, Lithuania.