A French-Iranian academic held in Iran for the past three years in a case that has raised tensions between Tehran and Paris has returned to prison after a brief furlough, her supporters said.
Fariba Adelkhah was last week allowed to leave Tehran's Evin prison for five days.
Hopes that the measure may be extended were not fulfilled, her support group said in a statement published late Sunday.
"Unfortunately, Fariba's five-day leave was not extended, or transformed into house arrest," it said. "It gave her a break, but it's still bad news."
Activists say that at least 20 foreign and dual nationals are being held by Tehran on baseless charges, in a deliberate policy of hostage diplomacy aimed at extracting concessions from the West.
Adelkhah's temporary release comes at a crucial time in the negotiations between world powers and Iran over the Iranian nuclear programme, with Tehran studying a final proposal from the EU aimed at salvaging a 2015 deal.
It is relatively common for prisoners in Iran to be allowed brief leave for time at home with families before returning to jail.
A specialist in Shiite Islam and a research director at Sciences Po university in Paris, Adelkhah was arrested in June 2019 along with her French colleague and partner Roland Marchal.
Adelkhah was sentenced in May 2020 to five years in prison for conspiring against national security, accusations her supporters say are absurd.
Marchal was released in March 2020 and Adelkhah was allowed home in Tehran in October 2020 with an electronic bracelet. But she was then sent back to prison in January 2022.
Iran last month allowed German-Iranian woman Nahid Taghavi, who was arrested in October 2020, a medical furlough to get treatment for back and neck problems.
Three other French nationals are also being held by Iran.
Benjamin Briere, who according to his family is simply a tourist, was arrested in May 2020 after taking pictures in a national park with a recreational drone and sentenced to eight years in prison on spying charges.
Meanwhile, French teachers' union official Cecile Kohler and her partner Jacques Paris were arrested in early May on security-related charges, Tehran has said.
Iran insists the foreigners are given fair trials but their families claim they are being held as pawns in a political game.