Russia has detained a U.S. citizen working for the Moscow bureau of The Wall Street Journal on suspicion of spying, drawing condemnation from the United States and press freedom groups. The newspaper swiftly denied the accusation.

Evan Gershkovich was on a reporting assignment in the Ural mountain city of Yekaterinburg when he was detained on Wednesday by agents from Russia's Federal Security Service, the FSB.

The FSB alleged in a statement that Gershkovich, "acting on an assignment from the American side, was gathering information classified as a state secret about the activity of one of the enterprises of Russia's military-industrial complex."

The Urals mountain region is home to various Russian military factories.

A Moscow court formally arrested the American reporter on charges of espionage and ordered him to be held until May 29 pending an investigation, according to Russian media reports, which said Gershkovich pleaded not guilty.

The Wall Street Journal said in a statement it "vehemently denies the allegations from the FSB and seeks the immediate release" of Gershkovich.

The U.S. is "deeply concerned"

U.S. officials say they are "deeply concerned" about the arrest.

"The targeting of American citizens by the Russian government is unacceptable. We condemn the detention of Mr. Gershkovich in the strongest terms," White House press secretary Karine Jean-Pierre said in a statement.

She said "the State Department has been in direct touch with the Russian government on this matter." Officials are also in contact with the reporter's family and his employer.

Secretary of State Antony Blinken also condemned "in the strongest possible terms" what he described as the "Kremlin's continued attempts to intimidate, repress, and punish journalists and civil society voices."

Russia has introduced a slew of restrictive laws surrounding media and information since Russian President Vladimir Putin launched an invasion of Ukraine in February 2022. At least 19 journalists were in Russian prison as of December, according to the Committee to Protect Journalists.

The Wall Street Journal is one of a small handful of Western media outlets that continue to report in Moscow despite the restrictive environment.

The Kremlin said it was aware of the arrest but called it "the prerogative" of the FSB.

"The only thing I can say is that, as far as we're aware, they caught him red-handed," Kremlin spokesmen Dmitry Peskov said in a call with reporters.

Peskov also noted that the Journal could continue its work in Russia.

Russia's Foreign Ministry — which issues visas and accreditation to foreign journalists — expressed support for Gershkovich's arrest.

"Unfortunately, it's not the first time the status of 'foreign correspondent', a journalist visa, and accreditation have been used by foreigners in our country to cover for activities that have nothing to do with journalism," Foreign Ministry spokeswoman Maria Zakharova said.

Russia's Kommersant daily newspaper said Gershkovich would soon be transported to Moscow's Lefortovo prison, the FSB's pre-trial detention facility.

Espionage charges in Russia can carry a prison sentence of up to 20 years.

Gershkovich, 31, has covered Russia since 2017, working with The Moscow Times and the Agence France-Presse before joining The Wall Street Journal's Moscow bureau in January 2022.

The New York-based Committee to Protect Journalists also called for Russian authorities to immediately release Gershkovich and drop charges against him.

Russia has "sent a clear message to foreign correspondents that they will not be spared from the ongoing purge of the independent media in the country," Gulnoza Said, CPJ's Europe and Central Asia program coordinator, said in a statement.

The U.S. warns citizens not to travel to Russia

Secretary of State Blinken reiterated the government's "strong warnings about the danger posed to U.S. citizens" inside Russia and said those in the country should leave immediately.

But White House National Security Council spokesman John Kirby said he did not know of U.S. government efforts to tell news organizations to remove their reporters from Russia. "We understand that you all have an important job to do," he said in a briefing Thursday.

Several Americans are detained in Russian prisons on charges ranging from drug smuggling to espionage.

In December, Russia and the U.S. engaged in a prisoner swap — trading American basketball star Brittney Griner, who had been sentenced to nine years in a penal colony for carrying a small amount of hash oil, for a convicted Russian arms dealer.