Iran has detained the father of an American man, who has been languishing in jail since the past four months. Baquer Namazi, 80, was arrested on 22 February in Tehran, his wife Effie Namazi said in a post on Facebook.

She said her husband is now in Evin Prison, where her son Siamak is also being held. However, even after repeated attempts Effie and a lawyer failed to get any information about Baquer and her son. She added that her husband suffered from "serious heart and other conditions" which require medication.

"Now both my innocent son Siamak and my Baquer are in prison for no reason. This is a nightmare I can't describe," Effie said. "I have been trying to find out more information but have been unable to do so. The lawyer also couldn't get any information or get to see him."

Siamak was visiting his family in Iran when he was arrested by the country's Islamic Revolutionary Guard Corps in October 2015. No formal charges were pressed against Siamak, reports suggest. Both Siamak and Baquer have dual US-Iranian citizenship.

"I am very familiar with this and I am engaged on it specifically, but I am not permitted due to privacy reasons to go into details here," US Secretary of State John Kerry said.

"We are aware of reports that a U.S. citizen was detained in Iran," State Department spokesman Mark Toner said, according to CBS News. "The U.S. Department of State has no higher priority than the protection of U.S. citizens overseas. We take our obligation to assist U.S. citizens abroad seriously," Toner added.

"I'm in a state of shock," Haleh Esfandiari, a friend of the family and a Mideast expert at the Wilson Center, said. "They want Siamak to make concessions that he wasn't willing to make," Esfandiari, who was detained in Iran for more than three months in 2007, averred.

Before settling down in the US in 1983, Baquer was governor of the oil-rich province of Khuzestan. He also served as a Unicef official and until recently and was running Hamyaran, an umbrella agency for Iranian non-governmental organisations. Siamak, is an Iranian-American businessman and was working for Crescent Petroleum in the United Arab Emirates.