Wall Street Journal reporter Evan Gershkovich appears in an undated handout image taken in an unknown location (Reuters)

Russian news agencies reported Friday that Moscow has formally charged US journalist Evan Gershkovich with espionage, adding that he had denied the indictment.

"FSB investigators charged Gershkovich with espionage in the interests of his country," Russian state-run agency TASS said, citing a law enforcement source.

"He categorically denied all accusations and stated that he was engaged in journalistic activities in Russia," TASS added.

Last week, CNN reported that Russia's Ambassador to the US, Anatoly Antonov, was summoned by the State Department over the arrest of Wall Street Journal's Moscow correspondent, Evan Gershkovich.

According to the report, citing a Biden administration official, Antonov met with Under Secretary for Political Affairs Victoria Nuland who reportedly told the envoy that Russia should release Gershkovich.

In response, Antonov read to Nuland Russia’s public statement on the reporter's case.

Evan Gershkovich was arrested last month after he was caught by Russia’s Federal Security Service while trying to obtain information classified as secret by the Russian government.

According to the FSB, Gershkovich, "acting on the instructions of the American side, collected information constituting a state secret about the activities of one of the enterprises of the Russian military-industrial complex."

Washington is reportedly preparing to designate Gershkovich as being "wrongfully detained"; a status that enables the government to deploy resources to lobby for his release.

Gershkovich’s arrest marks the first since the Cold War that a US reporter had been detained on charges of espionage.

The Wall Street Journal said it would seek retaliation over the matter, noting it would call US authorities to expulse Russian journalists and diplomats.

However, US President Joe Biden said he has no intention of doing so at present.

"That’s not the plan right now," the US President told reporters when asked if he is going to expel Russian diplomats.