KYIV, Ukraine—A prominent opponent of Belarus’ authoritarian president was arrested Sunday after the airliner in which he was traveling was diverted to the country after a bomb threat, in what the opposition is calling a hijacking operation by the government. The presidential press service said President Alexander Lukashenko personally ordered that a MiG-29 fighter jet accompany the Ryanair plane—carrying opposition figure Raman Pratasevich and traveling from Athens, Greece, to Vilnius, Lithuania—to the airport in the capital Minsk. Deputy air force commander Andrei Gurtsevich said the plane’s crew made the decision to land in Minsk, but Ryanair said in a statement that Belarusian air traffic control instructed the plane to divert to the capital. Lithuanian President Gitanas Nauseda also claimed the plane was forced to land in Minsk and said Lukashenko’s “regime is behind this.” The Belarusian Interior Ministry said Pratasevich was arrested at the airport. Pratasevich is a co-founder of …