Iran has indicted two French nationals and a Belgian for espionage and working against the country's national security, the semi-official Student News Network quoted a judiciary spokesperson as saying on Tuesday.
The agency did not give the names of the three or say where or when they were indicted.
Belgium's justice minister said last month Belgian aid worker Olivier Vandecasteele had been sentenced to 28 years in prison in Iran for what he called a "fabricated series of crimes".
Iranian media aired a video in October in which two French citizens appeared to confess to spying, amid recent unrest that Tehran has blamed on foreign foes. The video sparked outrage in France, which said the detainees were "state hostages".
A total of seven French citizens are being held in Iran, France's foreign minister said in November, a further sign of deteriorating relations between the two countries.
The Islamic Republic has accused foreign adversaries of fomenting a wave of unrest which erupted in Iran three months ago after the death in detention of 22-year-old Kurdish Iranian woman Mahsa Amini, who was arrested by morality police enforcing the Islamic Republic's mandatory dress code laws.
The protests mark one of the boldest challenges to the country's leadership since its 1979 Islamic Revolution and have drawn in Iranians from all walks of life.
(Reporting by Elwely Elwelly; editing by Alison Williams, Nick Macfie and Mark Heinrich)
