A Russian court on Tuesday extended the detention of Wall Street Journal reporter Evan Gershkovich by three months, according to a Russian state news agency.

Gershkovich was arrested in March in Yekaterinburg, Russia on espionage charges, which both the Journal and the State Department have denied.

The State Department designated Gershkovich as “wrongfully detained” by Russia in April. Secretary of State Antony Blinken has spoken with Russian Foreign Minister Sergey Lavrov to call for Gershkovich’s release, in a rare communication between high-level U.S. and Russian officials during Russia’s invasion of Ukraine.

The court decision that will now keep Gershkovich detained until Aug. 30 wasn’t announced in advance, and the entire case has been wrapped in secrecy.

Russian authorities haven’t detailed what — if any — evidence they have gathered to support the espionage charges. Various legal proceedings have been closed to the media, and no details immediately emerged about whether Gershkovich or U.S. Embassy representatives attended Tuesday’s hearing or what was said. The Russian state news agency Tass said the session was closed because the reporter was accused of possession of “secret materials.”

The Associated Press contributed to this report.