YEKATERINBURG, Russia, June 26 (Reuters) - U.S. journalist Evan Gershkovich went on trial behind closed doors on Wednesday in the Russian city of Yekaterinburg, where he faces charges of espionage and a likely sentence of up to 20 years in prison.

Prosecutors say the Wall Street Journal reporter gathered secret information on the orders of the U.S. Central Intelligence Agency about a company that manufactures tanks for Russia's war in Ukraine.

Gershkovich, his newspaper and the U.S. government all reject the allegations and say that he was just doing his job as a reporter accredited by the Foreign Ministry to work in Russia.

"This bogus accusation of espionage will inevitably lead to a bogus conviction for an innocent man," Wall Street Journal editor-in-chief Emma Tucker said in a letter to readers.

The U.S. embassy said in a statement: "His case is not about evidence, procedural norms, or the rule of law. It is about the Kremlin using American citizens to achieve its political objectives."

The Kremlin declined to comment on the opening of the trial. Spokesman Dmitry Peskov told reporters: "We know that this topic is very, very resonant in the United States, but it is not so resonant within our country."

After several hours of closed proceedings, the court said the next session would take place on Aug. 13 - an indication the case will drag on for months.

Journalists were briefly allowed to film the 32-year-old before the start of the trial, from which the media are barred.

The reporter was shaven-headed, in contrast to previous court appearances, and wore an open-necked shirt. He smiled and nodded at colleagues he recognised.

Prosecutor Mikael Ozdoyev spoke briefly to journalists to summarise the charges. "Gershkovich carried out the illegal actions while observing painstaking conspiratorial measures," he said.

Photo from Reuters