A French Irish citizen held in Iran since October 2022 and now on a dry hunger strike to protest his detention will survive no more than a few days unless he is freed, his sister said on Wednesday.

Bernard Phelan, a Paris-based travel consultant and one of seven French nationals held by Iran, was arrested in October while traveling and is being held in Mashhad in northeastern Iran.

The 64-year-old's family has said he started a dry hunger strike on Monday, refusing water. He has been refusing food since the start of the year.

His sister Caroline Masse-Phelan told AFP on Wednesday that her brother was an innocent man detained for reasons “beyond our comprehension.”

She said his health condition meant he had to be released urgently.

“It's a matter of days. He's an innocent man caught in the middle of I don't know what. He loves Iran, he is 64, sick, and wants to go home,” she said.

“He is showing serious signs of physical and psychological exhaustion,” said a French diplomatic source, adding he was in a “critical state.”

The Iranian authorities have refused to release Phelan on medical grounds despite repeated requests from the French and Irish authorities, the source said.

“I think he is part of a group of Europeans imprisoned for political reasons ... of which I know nothing,” his sister added. “We have nothing to do with this story.”

Phelan is one of two dozen foreigners held in Iran, according to activists, who describe the detainees as hostages seized to extract concessions from the West.

Phelan was traveling through Mashhad during the ongoing protests against Iran's clerical regime when he was arrested.

He is being held in Vakilabad prison in Mashhad. His sister said he suffers from a heart condition that requires medical treatment.

The hunger and thirst strikes are putting his life in danger but "he is doing this because he can't take it anymore,” she said.

“These are the only weapons,” she added, saying that it was on his urging that she had moved to make the case public.

Phelan is in contact with the crisis unit of the French foreign ministry, which passes on the messages from his family, but requests for direct communication with the family have been turned down by the Iranian authorities.

Phelan received his first French consular visit on January 9, after repeated requests, the diplomatic source added.

Activists fear that the current downgrading of contact between Western governments and Iran over the protest crackdown has lessened the prospect of the foreign detainees being released soon.

Siamak Namazi, a U.S. citizen of Iranian descent who was arrested in October 2015, this week started a seven-day hunger strike as he implored President Joe Biden to put greater priority on his case.

“Today the whole world is witnessing how atrociously this regime can respond to those who dare demand their basic rights," Namazi said.(AFP via VOA)

•PHOTO:French Irish citizen Bernard Phelan is seen in an undisclosed location in this undated photograph made available by his family on Jan. 18, 2023.