A Moscow court on Tuesday said jailed US journalist Evan Gershkovich would remain in pre-trial detention until at least March 30, ensuring he will spend at least a year behind bars in a Russian jail.

Russian prosecutors have charged Wall Street Journal reporter Gershkovich with espionage -- the first time such a criminal accusation has been levelled against a Western reporter in Russia since the fall of the Soviet Union.

Gershkovich, his employers and the White House all reject the charges, which carry a maximum sentence of 20 years.

"Gershkovich will remain in custody until March 30, 2024," the Moscow courts service said in a statement Tuesday following a hearing at the Moscow City Court.

The appeal was a technical challenge against an earlier decision to extend Gershkovich's pre-trial detention. It did not concern the substance of the case.

His shock arrest by FSB counterintelligence agents in the Urals city of Yekaterinburg last March while on a reporting trip triggered uproar in Washington.

And the United States has slammed the Kremlin over his ongoing detention, which will hit the one-year mark on March 29.

"The charges against Evan are baseless. The Russian government has locked Evan up simply for reporting news," US Ambassador to Russia Lynne Tracy, who attended the hearing, said outside the court Tuesday.

President Vladimir Putin said earlier this month he would like to see Gershkovich released as part of a prisoner exchange.

In remarks to conservative American TV commentator Tucker Carlson, he said talks between Russia and the United States about a possible swap were ongoing.

The Russian leader made clear he wanted any deal to involve the release of a Russian jailed in Germany for killing a Chechen dissident.

'Bargaining chips'

Washington has accused Moscow of arresting American citizens on baseless charges to use them as "bargaining chips" to secure the release of Russians convicted abroad.

Former US marine Paul Whelan, in prison in Russia since 2018 and serving a 16-year sentence on espionage charges, is also pushing to be included in any future prisoner exchange.

"The United States will not rest until Evan and Paul are free and back home in the United States with their families," Tracy said.

Separately on Tuesday, Russia's FSB security service said it had arrested a 33-year-old dual US-Russian citizen in Yekaterinburg -- the same city where Gershkovich was arrested -- on suspicion of treason.

It said the woman, a Los Angeles resident, had been helping Ukrainian organisations collect funds "to purchase tactical medical items, equipment, means of destruction and ammunition for the Ukrainian armed forces".

The FSB said she had been acting "against the security of our country" and had been supporting the Ukrainian army while in the United States.

Treason is punishable by up to life in prison under legislation toughened since the start of Russia's military offensive against Ukraine.

The supreme court of Russia's Tatarstan region also rejected an appeal Tuesday by jailed US-Russian journalist Alsu Kurmasheva to be transferred from pre-trial detention to house arrest, her employers reported.

Kurmasheva, a Radio Free Europe/Radio Liberty (RFE/RL) editor who lives in Prague, had her passports confiscated and was arrested in October while back in Russia for a family emergency.

She faces charges of failing to register as a "foreign agent" and contravening Russia's strict military censorship laws, her employers say.

RFE/RL reported Tuesday that the Tatarstan Supreme Court ordered she be held in jail until at least April 4, rejecting an appeal lodged on health grounds that called for her to be sent to house arrest.

© Agence France-Presse