PARIS (AP) — France on Thursday called for the “immediate release” of seven French nationals detained in Iran, denouncing an “unjustifiable and unacceptable” situation.

French “hostages” in Iran include 35-year-old Louis Arnaud, foreign ministry spokesperson Anne-Claire Legendre said.

Arnaud, whose name has just been made public, was arrested on Sept. 28 as he was traveling in Iran “for touristic reasons,” she said. He is being detained in “very difficult conditions” in the Tehran prison of Evin, where France’s ambassador to Iran was able to meet him on Dec. 11, she added.

Foreign Minister Catherine Colonna on Wednesday discussed the issue in a phone call with her Iranian counterpart Hossein Hossein Amirabdollahian, the French foreign ministry said.

“We are especially worried about Bernard Phélan given his health condition,” Legendre said. The foreign ministry has said that the French-Irish citizen, detained in Iran since October, needs “appropriate medical care that is not provided” in prison.

Iran has detained a number of foreigners and dual nationals over the years, accusing them of espionage or other state security offenses and sentencing them after secretive trials in which rights groups say they are denied due process.

Families and support committees of Arnaud and other French people jailed in Iran, including Fariba Adelkhah, Benjamin Brière and Cécile Kohler, have called for a gathering on Saturday in Paris.

A separate event has been organized in Paris that day in support for Belgian national Olivier Vandecasteele by Doctors without Borders. The aid worker, who worked for the nongovernmental organization for many years, was arrested in Tehran in February last year. Doctors without Borders says the conditions of his detention are putting his life at risk.