MOSCOW (AP) — A Wall Street Journal reporter detained on espionage charges in Russia is appearing in court to appeal his extended detention.

U.S. citizen Evan Gershkovich, 31, was arrested in late March while on a reporting trip. A Moscow court agreed last month to keep him in custody until Aug. 30. Defense lawyers challenged the decision, and the Moscow City Court is scheduled to hear the appeal on Thursday.

Gershkovich and his employer have denied he spied in Russia. The U.S. government has declared him to be wrongfully detained and demanded his immediate release.

His arrest in the city of Yekaterinburg rattled journalists in Russia, where authorities have not detailed what, if any, evidence they have gathered to support the espionage charges.

Gershkovich is being held at Moscow’s Lefortovo prison, which is notorious for its harsh conditions. U.S. Embassy officials were allowed to visit him once, but Russian authorities rejected two other requests to see him.

Russian Deputy Foreign Minister Sergei Ryabkov told reporters on Thursday that the ministry is considering another visit request from the embassy.