Russia’s top security agency arrested an American reporter for the Wall Street Journal on espionage charges, the first time a U.S. correspondent was put behind bars on spying accusations since the Cold War. The newspaper denied the allegations against Evan Gershkovich.

The Federal Security Service said Thursday that Gershkovich was detained in the Ural Mountains city of Yekaterinburg while allegedly trying to obtain classified information.

The FSB, which is the top successor agency to the Soviet-era KGB, alleged that Gershkovich “was acting on the U.S. orders to collect information about the activities of one of the enterprises of the Russian military industrial complex that constitutes a state secret.”

The Wall Street Journal said it “vehemently denies the allegations” and is seeking Gershkovich’s immediate release. “We stand in solidarity with Evan and his family,” the paper said.

The arrest comes amid bitter tensions between the West and Moscow over its war in Ukraine.

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. He was released without charges 20 days later in a swap for an employee of the Soviet Union’s United Nations mission who was arrested by the FBI.

The FSB didn’t say when the arrest took place. Gershkovich, who covers Russia, Ukraine and other ex-Soviet nations as a correspondent in the Wall Street Journal’s Moscow bureau, could face up to 20 years in prison if convicted of espionage.

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

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

Gershkovich’s arrest follows a swap in December, in which 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.