"Let him go," the US president told the Russian government, in front of journalists who were asking, at the White House, his first public reaction on this case.

Evan Gershkovich, a 31-year-old Russian-speaking reporter known for his rigour, was arrested in Yekaterinburg, in the Urals, on suspicion of "espionage".

"The timing of the arrest looks like a calculated provocation to embarrass the United States and intimidate the foreign press that is still working in Russia," he added.

The Kremlin on Thursday warned Washington against any form of retaliation targeting Russian media working in the United States after the arrest of the American journalist caught, according to Moscow, "in flagrante delicto" of espionage.

"Regarding the demand for the expulsion of all Russian journalists, the newspaper (the WSJ) can say that, but it should not happen. There is simply no reason for this," Kremlin spokesman Dmitry Peskov told reporters on Friday. He added that the American journalist "was caught red-handed (espionage)" and that "the situation is clear."

Evan Gershkovich denied the charges against him during a hearing in a Moscow court, according to Russia's state-run Tass news agency. The American journalist has nevertheless been remanded in custody until 29 May, a measure that can be extended pending a possible trial.

American journalist Evan Gershkovich (c), accused of spying by Russia, is escorted out of the Lefortovsky court, on March 30, 2023 in Moscow © Kirill KUDRYAVTSEV / AFP

According to Tass, the case has been classified as "secret", which restricts the publication of information about him.

The only details available at this stage: the FSB announced that it had "foiled illegal activity" by arresting Evan Gershkovich in Yekaterinburg, on an unspecified date.

His arrest comes amid increased repression in Russia against the press since the offensive against Ukraine, which has strained relations between Moscow and Washington.

It also follows an exchange in December between American basketball star Brittney Griner, who was in custody in Russia, and Russian arms dealer Viktor Bout, a prisoner in the United States.

American journalist Evan Gershkovich, July 24, 2021 in an unspecified © location Dimitar DILKOFF / AFP / Archives

The White House slammed an arrest "unacceptable" and its spokeswoman, Karine Jean-Pierre, called the accusation of espionage "ridiculous", while the head of US diplomacy Antony Blinken said he was "extremely concerned".

The European Union, through its head of diplomacy Josep Borrell "condemns" the detention of Evan Gershkovich by Russia, in a tweet that denounces Moscow's "systematic contempt" for press freedom.

© 2023 AFP