A Moscow court has rejected an appeal by Wall Street Journal reporter Evan Gershkovich and upheld an earlier ruling that he should remain in jail on espionage charges until late August.

The 31-year-old US citizen was arrested in late March while on a reporting trip.

A Moscow court agreed last month to keep him in custody until August 30.

Defence lawyers had challenged the decision.

Gershkovich, wearing a black T-shirt and light blue jeans, looked tense and paced around inside a glass defendant’s cage while waiting for the hearing to begin at the Moscow City Court.

Before the hearing began, other journalists in the courtroom were asked to leave and the proceedings took place behind closed doors.

Gershkovich’s parents and US ambassador to Russia Lynne Tracy attended the hearing.

Speaking to reporters afterwards, Ms Tracy said that “Evan continues to show remarkable strength and resilience in these very difficult circumstances”.

Ms Tracy said she was “extremely disappointed” by the ruling, reiterating that Gershkovich was “an innocent journalist” and Russia’s charges against him were baseless.

“Such hostage diplomacy is unacceptable, and we call on the Russian Federation to release him,” she said.

The Wall Street Journal said in a statement after the hearing that Gershkovich “has been wrongfully detained for more than 12 weeks for nothing more than doing his job as a journalist”, and it again called for his immediate release.

Gershkovich and his employer have denied he spied in Russia.

The US 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.

US 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.