MOSCOW - Russia's security service arrested an American reporter for The Wall Street Journal on espionage charges, the first time a U.S. correspondent has been detained on spying accusations since the Cold War. The newspaper denied the allegations and demanded his release.

Evan Gershkovich, 31, was detained in Yekaterinburg, Russia's fourth-largest city, about 1,670 kilometers (1,035 miles) east of Moscow. Russia's Federal Security Service accused him of trying to obtain classified information.

Known by the acronym FSB, the service is the top domestic security agency and main successor to the Soviet-era KGB. It alleged that Gershkovich “was acting on instructions from the American side to collect information about the activities of one of the enterprises of the Russian military-industrial complex that constitutes a state secret.”

The Journal “vehemently denies the allegations from the FSB and seeks the immediate release of our trusted and dedicated reporter, Evan Gershkovich,” the newspaper said. “We stand in solidarity with Evan and his family.”

The arrest comes at a moment of bitter tensions between the West and Moscow over its war in 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.

Earlier this week, a Russian court convicted a father over social media posts critical of the war and sentenced him to two years in prison. His 13-year-old daughter was sent to an orphanage.

Gershkovich is the first American reporter to be arrested on espionage charges in Russia since September 1986, when Nicholas Daniloff, a Moscow correspondent for U.S. News and World Report, was arrested by the KGB. 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.

At a hearing Thursday, a Moscow court quickly ruled that Gershkovich would be kept behind bars pending the investigation.

While previous American detainees have been freed in prisoner swaps, a top Russian official said it was too early to talk about any such deal.

In Washington, the Biden administration said it had spoken with the Journal and Gershkovich's family. White House press secretary Karine Jean-Pierre condemned the arrest “in the strongest terms” and urged Americans to heed government warnings not to travel to Russia.

The State Department was in direct touch with the Russian government and seeking access to Gershkovich, Jean-Pierre said. The administration has no “specific indication” that journalists in Russia are being targeted, she said.

Gershkovich, who covers Russia, Ukraine and other ex-Soviet nations as a correspondent in the Journal's Moscow bureau, could face up to 20 years in prison if convicted of espionage. Prominent lawyers noted that past investigations into espionage cases took a year to 18 months, during which time he may have little contact with the outside world.

The FSB noted that Gershkovich had accreditation from the Russian Foreign Ministry to work as a journalist, but ministry spokeswoman Maria Zakharova alleged that Gershkovich was using his credentials as cover for “activities that have nothing to do with journalism.”

Kremlin spokesman Dmitry Peskov told reporters: “It is not about a suspicion, it is about the fact that he was caught red-handed.”

Gershkovich speaks fluent Russian and had previously worked for the French news agency Agence France-Presse and The New York Times. He was a 2014 graduate of Bowdoin College in Maine, where he was a philosophy major who cooperated with local papers and championed a free press, according to Clayton Rose, the college's president.

His last report from Moscow, published earlier this week, focused on the Russian economy's slowdown amid Western sanctions imposed after Russian troops invaded Ukraine last year.

Ivan Pavlov, a prominent Russian defense attorney who has worked on many espionage and treason cases, said Gershkovich's case is the first criminal espionage charge against a foreign journalist in post-Soviet Russia.

“That unwritten rule not to touch accredited foreign journalists, has stopped working,” said Pavlov, a member of the First Department legal aid group.

Pavlov said the case against Gershkovich was built to give Russia “trump cards” for a future prisoner exchange and will likely be resolved “not by the means of the law, but by political, diplomatic means.”

Russian Deputy Foreign Minister Sergei Ryabkov ruled out any quick swap.

“I wouldn't even consider this issue now because people who were previously swapped had already served their sentences,” Ryabkov said, according to Russian news agencies.

In December, WNBA star Brittney Griner was freed after 10 months behind bars in exchange for Russian arms dealer Viktor Bout.

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

“Our family is sorry to hear that another American family will have to experience the same trauma that we have had to endure for the past 1,553 days,” Whelan's brother David said in an emailed statement. “It sounds as though the frame-up of Mr. Gershkovich was the same as it was in Paul's case.”

Jeanne Cavelier, of the press freedom group Reporters Without Borders, said Gershkovich's arrest “looks like a retaliation measure of Russia against the United States.”

“We are very alarmed because it is probably a way to intimidate all Western journalists that are trying to investigate aspects of the war on the ground in Russia,” said Cavelier, head of Eastern Europe and Central Asia desk at the Paris-based group.

Another prominent lawyer with the First Department group, Yevgeny Smirnov, said that those arrested on espionage and treason charges are usually held at the FSB's Lefortovo prison, where they are usually placed in total isolation, without phone calls, visitors or even access to newspapers. At most, they can receive letters, often delayed by weeks. Smirnov called these conditions “tools of suppression.”

Smirnov and Pavlov both said that any trial would be held behind closed doors. According to Pavlov, there have been no acquittals in treason and espionage cases in Russia since 1999.