STORY: Ties between France and Iran have deteriorated in recent months with Tehran detaining seven of its nationals in what Paris has also described as arbitrary arrests that are equivalent to state hostage taking.

"We don't have any other choice than staying hopeful. I think we have to stay hopeful but it is very difficult, it has already been much too long. For Benjamin, it's been 2.5 years,” the sister of detained French national Benjamin Briere, Blandine Briere, said.

France's foreign ministry demanded on Thursday (January 26) the immediate release of Bernard Phelan, a Franco-Irish citizen detained in Iran whose health situation has worsened with Paris saying he has been denied urgent medical care, along with six other French detainees.

French authorities said they held Tehran responsible for the health of all its citizens.