France, Aug. 21 -- French researcher Laurent Vinatier, who is already serving time in a Russian prison, is now facing espionage charges that could extend his sentence by up to 20 years.

Vinatier is to appear at a hearing on Monday to face new charges of espionage, which carry a sentence of up to 20 years in prison, according to court documents reported by Russian news agencies.

Vinatier, who worked for a Swiss conflict mediation organisation, is currently serving a three-year prison sentence after he was convicted in October of violating Russian laws requiring individuals deemed "foreign agents" to register, and was accused of gathering military information of value to foreign intelligence services.

His appeal against the sentence was ...