KYIV, Ukraine—The chief editor of a popular Internet news site in one of Belarus’ largest cities was detained and his residence searched amid a crackdown on independent journalists and opponents of authoritarian President Alexander Lukashenko. Police said Sunday they were investigating Hrodna.life editor Aliaksei Shota on suspicion of extremism. The publication focuses on Belarus’ fifth-largest city Grodno. City police said the website “posted information products that were duly recognized as extremist,” but did not give details. The website said he was held by police for several hours before being released, and that computer hard drives were taken by police from his home. Shota has collaborated with the country’s most popular internet portal Tut.by, which authorities closed this month after arresting 15 employees. Belarus’ crackdown escalated a week ago with the arrest of dissident journalist Raman Pratasevich and his girlfriend who were aboard a commercial flight that was diverted to the …