Jailed Wall Street Journal reporter Evan Gershkovich has been charged with espionage in Russia and has entered a formal denial, two Russian news agencies reported.

The state news agency Tass and the Interfax news agency said a law enforcement source had told them that the Federal Security Service (FSB) had officially charged the American journalist.

The news outlets did not say in what form he was formally charged or when it happened, but suspects are generally presented with a paper outlining the accusations.

In the Russian legal system, the filing of charges and a response from the accused represents the formal start of a criminal investigation, initiating what could be a long and secretive judicial process.

Russia Reporter Arrested
Journalists at an entrance to Lefortovo prison in Moscow (Alexander Zemlianichenko/AP)

Tass quoted its source as saying: “The FSB investigation charged Gershkovich with espionage in the interests of his country. He categorically denied all accusations and stated that he was engaged in journalistic activities in Russia.”

Russian authorities arrested Mr Gershkovich, 31, in Yekaterinburg, Russia’s fourth-largest city, on March 29. He is the first US correspondent since the Cold War to be detained for alleged spying.

The FSB specifically accused him of trying to obtain classified information about a Russian arms factory. The Wall Street Journal has denied the accusations.

The case has caused an international uproar. On Thursday, the USambassador to Russia and a top Russian diplomat met to discuss it.

In the meeting with US ambassador Lynne T Tracy, Russian deputy foreign minister Sergei Ryabkov stressed “the serious nature of the charges” against Mr Gershkovich, according to a Russian Foreign Ministry statement.

The statement repeated earlier Russian claims that the reporter “was caught red-handed while trying to obtain secret information, using his journalistic status as a cover for illegal actions”.

Lawyers representing Mr Gershkovich met him on Tuesday for the first time since his detention, according to Wall Street Journal editor-in-chief Emma Tucker.

She said the reporter was in good health and was “grateful for the outpouring of support from around the world. We continue to call for his immediate release”.

Mr Gershkovich was ordered held behind bars for two months in Russia pending an investigation. A Moscow court said on Monday that it had received a defence appeal against his arrest which is scheduled to be heard on April 18.

The charges emerged after the US Senate’s top two leaders demanded that Moscow immediately release Mr Gershkovich in a rare bipartisan statement that condemned his detention and declared that “journalism is not a crime”.

The statement from Senate majority leader Chuck Schumer and minority leader Mitch McConnell came as the US works to end what it calls the unlawful detention of Mr Gershkovich, the first journalist to be held on alleged espionage since the Cold War.

“We strongly condemn the wrongful detention of US citizen and Wall Street Journal reporter Evan Gershkovich, and demand the immediate release of this internationally known and respected independent journalist,” the two men said.

They said Mr Gershkovich had been accredited by the Russian Ministry of Foreign Affairs to work as a journalist in Russia and “Russian authorities have failed to present any credible evidence to justify their fabricated charges”.

Mr Schumer and Mr McConnell wrote: “Let there be no mistake: journalism is not a crime.”

Mr Gershkovich, 31, is being held in a Moscow prison.

The son of immigrants from the Soviet Union, he grew up speaking Russian at home in Princeton, New Jersey. Russia’s top security agency said he was trying to obtain classified information about a Russian arms factory.

President Joe Biden told reporters last Friday that his message to Russia was: “Let him go.”