French Foreign Minister Jean-Yves Le Drian on Sunday urged Iran to free two French nationals held in Evin prison in Tehran since last June, who are unwell.
Roland Marchal is a senior researcher at the Sciences Po university in Paris and Fariba Adelkhah, a Franco-Iranian dual national, is also an academic there.
Authorities dropped spying charges against Ms Adelkhah but are still holding her on other security-related charges, her lawyer said on January 7.
He said Mr Marchal was being held on suspicion of acting against Iranian national security.
"We consider these detentions intolerable," Mr Le Drian told broadcasters LCI and RTL and the newspaper Le Figaro.
"We have made this known to the highest authorities, including President [Hassan] Rouhani.
“We know that they are not in a very good condition and that they are not always being treated well. We think Iran would give a strong signal by releasing them.”
Le Figaro reported in January that Ms Adelkhah had been on hunger strike since December 24 and was in extremely poor health, while Mr Marchal was "very unstable".
The academics’ university association said Mr Marchal, an Africa expert, was arrested at Tehran airport as he arrived to spend the Eid religious holiday with Ms Adelkhah in Iran.
Tension increased further in the region last month after the US killed Iran’s most senior military general, Qassem Suleimani, in a drone strike in Baghdad.
British-Australian academic Kylie Moore-Gilbert, a lecturer in Islamic studies at the University of Melbourne, is also being held in Evin Prison after being arrested in September 2018 on charges of espionage.
Nazanin Zaghari-Ratcliffe, a British-Iranian dual national, has been detained in the same jail since her arrest in 2016 over spying allegations, which she denies.
The British Foreign Office has said it is “extremely concerned” about British dual nationals detained in Iran.
Britain and France have advised its citizens against all travel to Iran.
