Russian prosecutors have filed espionage charges against Wall Street Journal reporter Evan Gershkovich, according to Russian news agencies Interfax and TASS.

The American newspaper’s correspondent pleaded not guilty, “categorically” denying the charges against him, Interfax and TASS news agency reported.

Gershkovich, an American citizen of Russian descent, was arrested last week in the Urals city of Yekaterinburg on espionage charges that the Wall Street Journal, Western leaders, and his colleagues have called false.

According to Interfax, Gershkovich is being prosecuted under Article 276 of the Russian Criminal Code, a charge that carries a 20-year prison sentence.