US journalist Evan Gershkovich has been formally charged with spying in Russia, according to local media.
Gershkovich, an experienced Russia reporter, was arrested last week in the city of Yekaterinburg while working for the Wall Street Journal (WSJ).
The media reports said he categorically rejected the accusations against him. The newspaper has demanded his immediate release.
Following his arrest, the Kremlin said he had been caught “red-handed”.
Mr Gershkovich, 31, is well known among foreign correspondents in Moscow and BBC Russia Editor Steve Rosenberg describes him as an excellent reporter and a highly principled journalist.
The White House condemned his detention “in the strongest terms”.