The trial of Washington Post correspondent Jason Rezaian on espionage charges opened behind closed doors in Tehran on Tuesday, Iran's ISNA news agency reported.

Rezaian, 39, is accused of "espionage, collaboration with hostile governments, gathering classified information and disseminating propaganda against the Islamic republic," according to his lawyer Leila Ahsan.

She has condemned the charges saying there is "no justifiable proof" to substantiate them.