An opposition activist and advocate of a referendum against corrupt public officials has been detained in Moscow after being summoned by police for questioning on December 17.
The detainee, Kirill Barabash, is an active member of the Initiative Group For Holding The Referendum (IGPR).
Barabash's wife, Daria Kucheryavaya, says her husband was summoned by police a day after investigators searched their apartment.
She said Barabash is suspected in a case linked to extremism.
The IGPR used to be called the Army of the People's Will (ANF) before the group was branded as extremist in 2010 and banned in Russia.
Three other IGPR members in Moscow were charged with membership in a banned organization during the summer of 2015. Two are currently in pretrial detention and one is under house arrest.
The Moscow-based Memorial Human Rights Center has described the three -- Aleksandr Sokolov, Yury Mukhin, and Valery Parfyonov -- as prisoners of conscience.