A Russian court convicted four journalists of extremism Tuesday for working for an anti-corruption group founded by the late opposition leader Alexei Navalny and sentenced them to 5 1/2 years in prison each.

Antonina Favorskaya, Kostantin Gabov, Sergey Karelin and Artyom Kriger were found guilty of involvement with a group that had been labeled as extremist. All four maintained their innocence, arguing they were being prosecuted for doing their job as journalists.

The closed-door trial was…