Wall Street Journal reporter Evan Gershkovich has appealed against a Russian court decision to extend his pre-trial detention by three months, court data showed on Friday.
Gershkovich, a U.S. citizen, was arrested in March on espionage charges after Russia's FSB security service accused him of collecting military secrets in the city of Yekaterinburg.
He was initially remanded in custody until May 29, but a court on Tuesday extended his detention in a closed hearing until Aug. 30.
The United States says he has been wrongfully detained and has called for his immediate release.