A Russian judge on Tuesday upheld the detention of jailed American journalist Evan Gershkovich, who was arrested on spying charges as part of a sweeping Kremlin crackdown on dissent and press freedom amid the war in Ukraine. He and the U.S. government vehemently deny the allegations.

The Wall Street Journal reporter is the first U.S. correspondent since the Cold War to be detained in Russia on spying allegations and his arrest rattled journalists in the country and elicited outrage in the West. Dozens of journalists crowded into the courtroom to catch a glimpse of Gershkovich, who looked calm as he stood inside a glass cage.

Russia’s Federal Security Service detained the 31-year-old in Yekaterinburg in March and accused him of trying to obtain classified information about a Russian arms factory.

Gershkovich, his employer and the U. S. government deny he was involved in spying and have demanded his release.

“Evan is a member of the free press who right up until he was arrested was engaged in newsgathering. Any suggestions otherwise are false," the Journal has said in a statement.

Last week, the U.S. officially declared that Gershkovich was “wrongfully detained.”

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A judge with the Moscow City Court rejected the reporter's appeal of his detention on Tuesday, ruling that he must stay in jail pending an investigation and trial.

Gershkovich could face up to 20 years in prison if convicted. Russian lawyers have said past investigations into espionage cases took a year to 18 months, during which time he could have little contact with the outside world.

He has been held in Moscow’s Lefortovo prison, which dates from the czarist era and has been a terrifying symbol of repression since Soviet times.

The arrest comes at a moment of bitter tensions between the West and Moscow over its invasion of Ukraine and as the Kremlin intensifies a crackdown on opposition activists, independent journalists and civil society groups.

The sweeping campaign of repression is unprecedented since the Soviet era. Activists say it often means the very profession of journalism is criminalized, along with the activities of ordinary Russians who oppose the war.

Last month, a Russian court convicted a father over social media posts critical of the war and sentenced him to two years in prison. On Monday, a Russian court convicted top opposition figure Vladimir Kara-Murza Jr. of treason for publicly denouncing the war and sentenced him to 25 years in prison.

The U.S. has pressed Moscow to grant consular access to Gershkovich. U.S. Ambassador Lynne Tracy, who attended Tuesday's hearing, said a day earlier that she had visited Gershkovich in prison. She said on Twitter that “he is in good health and remains strong,” reiterating a U.S. call for his immediate release.

U.S. President Joe Biden spoke to Greshkovich’s parents last week and again condemned his detention.

“We’re making it real clear that it’s totally illegal what’s happening, and we declared it so,” he said.

Gershkovich is the first American reporter to be arrested on espionage charges in Russia since 1986, when Nicholas Daniloff, a Moscow correspondent for U.S. News and World Report, was arrested. Daniloff was released without charge 20 days later in a swap for an employee of the Soviet Union’s United Nations mission who was arrested by the FBI, also on spying charges.

A top Russian diplomat said last week that Russia might be willing to discuss a potential prisoner swap with the U.S. involving Gershkovich after his trial. That means any exchange is unlikely to happen any time soon.

In December, American basketball star Brittney Griner was exchanged for Russian arms dealer Viktor Bout following her trial and conviction on drug possession charges. She had been sentenced to nine years in prison and ended up spending 10 months behind bars.

Another American, Michigan corporate security executive Paul Whelan, has been imprisoned in Russia since December 2018 on espionage charges, which his family and the U.S. government have called baseless.