The Iran-Based United Nations human rights investigator called on Friday for the immediate release of three Iranians with dual nationality whose health after imprisonment had become a matter of concern.

Ahmed Shaheed, U.N. special rapporteur on the situation of human rights in Iran, highlighted the case of the Iranian-British aid worker Nazanin Zaghari-Ratcliffe. Zaghari-Ratcliffe was arrested in April along with her 2-year-old daughter and put on trial in August.

An Iranian ultra-conservative revolutionary court sentenced her to five years in prison on charges that remain secret, her family said last month.

“Sentencing individuals for charges that are kept secret from defendants and their defense lawyers is a mockery of justice,” Shaheed, a former foreign minister of the Maldives, said in a statement. He said her health had also “seriously deteriorated” since her arrest.

Zaghari-Ratcliffe works for the Thomson Reuters Foundation, a London-based charity that is independent of Thomson Reuters and operates independently of its news arm, Reuters News. Her daughter, now also trapped in Iran, is being looked after by Zaghari-Ratcliffe’s parents.

Iran’s ultra-conservative Revolutionary Guards have accused Zaghari-Ratcliffe of trying to overthrow Iran’s clerical establishment, an accusation that the Foundation and her husband have dismissed.

“I am convinced of Nazanin’s innocence,” Thomson Reuters Foundation Chief Executive Monique Villa said in a statement. “She had no dealings with Iran whatsoever in her professional capacity as the Thomson Reuters Foundation does not operate in Iran, directly or indirectly.”

Shaheed said that two elderly men held in Tehran’s Evin prison required urgent medical attention and must also be freed.

Baquer Namazi, an 80-year-old who also holds American nationality, has been detained since February on unknown charges and without access to a lawyer, he said.

Kamal Foroughi, 77, is an Iranian-British businessman arrested in May 2011 who is serving an eight-year prison term on charges of espionage and possession of alcoholic beverages, he said.

Shaheed welcomed the release last month of Homa Hoodfar, an Iranian-Canadian national arrested in June. The Montreal academic was released a week after the two countries began talks on a restoration of diplomatic ties, broken off in 2012.