(Reuters) -A Moscow court has arrested an already imprisoned Russia-born U.S. citizen on charges of espionage, Russian news agencies reported on Thursday.

The businessman, Gene Spector, is serving a 3.5-year sentence after pleading guilty in 2022 to his role in bribing an assistant of ex-Russian Deputy Prime Minister Arkady Dvorkovich, according to the state news agency, TASS.

Spector was born in Russia's St. Petersburg and then moved to the United States. Before his 2021 arrest, he served as chairman of the board of Medpolymerprom Group, a company specialising in cancer curing drugs, TASS said.

Russian news agencies did not report any details of the new charges, but said the court session was held behind closed doors as the case materials were classified.

Speaking on CNN, White House spokesperson John Kirby said the administration was still collecting information about the case and had no comment yet. The State Department did not immediately respond to a request for comment.

(Reporting by Maxim Rodionov, Kanishka Singh and Lidia Kelly; Editing by Chris Reese, Daniel Wallis and Raju Gopalakrishnan)