On Friday, Joe Biden, the president of the United States, urged Russia to free detained Wall Street Journal correspondent Evan Gershkovich, who was charged with spying by Moscow.

The most serious public action against a foreign journalist since Russia invaded Ukraine, the FSB security agency of Russia announced on Thursday that it had detained Gershkovich.

As Biden departed the White House for a visit to storm-devastated Mississippi, he said, “Let him go”.

When asked if he intended to expel Russian ambassadors following Gershkovich’s detention, Biden responded, “That’s not the plan right now”.

Karine Jean-Pierre, the White House press secretary, called the espionage allegations “ridiculous” and said there was no proof to back them up.

According to the Wall Street Journal, false accusations were used to justify Gershkovich’s arrest.

The FSB charged Gershkovich with collecting details about a military factory that were considered state secrets.

The 31-year-old journalist was detained in Yekaterinburg, a city in the Urals, as he attempted to obtain classified material, according to the statement, which did not mention the factory’s name or location. It did not offer written or visual proof of his culpability.