Moscow, Russia - Lawyers acting for Evan Gershkovich, the Wall Street Journal correspondent being held for allegedly spying by Russia, have lodged a formal objection to his detention, a spokesman for the district court in Lefortovo to the east of Moscow said on Monday.

The court had received documentation from the lawyers, the spokesman said, according to a report by the Interfax news agency.

Gershkovich, who works for the Wall Street Journal newspaper, was arrested in Ekaterinburg to the east of Moscow by Russia's FSB intelligence service on Thursday.

He has been detained provisionally up to May 29, but could face a 20-year sentence if found guilty of espionage.

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US Secretary of State Antony Blinken demanded the journalist's release in a phone call with Russian Foreign Minister Sergey Lavrov on Sunday.

President Joe Biden has personally called for his release, and the White House has termed the charges "ridiculous."

The Wall Street Journal has strongly denied all allegations against Gershkovich.

Kremlin spokesman Dmitri Peskov claimed that Gershkovich had been caught "red-handed" spying for the United States.

At the time of his arrest, Gershkovich was trying to write a report about the population's attitude toward the Wagner army's recruitment attempts, according to media reports.

The private contractor is deployed in Russia's war against Ukraine, which Moscow started 13 months ago.

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Since Russia invaded Ukraine 13 months ago, Moscow has significantly restricted freedom of expression and freedom of the press in the country.

There is also the threat of legal proceedings for discrimination or damage to the reputation of the Russian army.

Some correspondents and media had temporarily stopped working last year after the war began for fear of repression.

The number of Western journalists has also decreased because many media outlets are unable to get their reporters accredited in Russia.