Moscow (AFP) - 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, as Russia separately slapped a ban on a US-funded broadcaster.

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 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.

March 29 will mark one year since Gershkovich's shock arrest by FSB counterintelligence agents in the Urals city of Yekaterinburg.

"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. 

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.

Banning US-funded broadcaster

Russia separately on Tuesday banned US-funded Radio Free Europe/ Radio Liberty (RFE/RL), putting its staff and contributors at risk of prosecution.

The outlet's name was listed on the Ministry of Justice database as an "undesirable organisation".

In Washington, State Department spokesman Matthew Miller said the move curbed freedom of speech.

"It is quite clear that they do not want their people to have information about what the Russian regime does abroad, what the Russian regime does to its own people," Miller told reporters.

RFE/RL president Stephen Capus said the move was "the latest example of how the Russian government views truthful reporting as an existential threat". 

"Millions of Russians have relied on us for decades –- including record-breaking audiences over the past few days since the death of Alexei Navalny –- and this attempt to stifle us will only make RFE/RL work harder to bring free and independent journalism to the Russian people," he said, referring to the death in an Arctic prison of one of Putin's loudest critics.

Also on Tuesday, the supreme court of Russia's Tatarstan region rejected an appeal by a jailed RFE/RL editor, US-Russian journalist Alsu Kurmasheva, to be transferred from pre-trial detention to house arrest, her employers reported.

Kurmasheva, 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 said the court ordered Kurmasheva to be held in jail until at least April 4, rejecting the appeal, which had been lodged on health grounds.

'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".

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