The wife of Baquer Namazi wrote in a Facebook post on Wednesday that her husband was arrested late on Monday and is now being held in Tehran's Evin prison. Her son Siamak (pictured above) is also currently detained there.

"Now both my innocent son Siamak and my Baquer are in prison for no reason. This is a nightmare I can't describe," Effie Namazi wrote in her post, adding that she was "extremely concerned" for Baquer's health, as he has a serious heart condition.

The 80-year-old Baquer, a former provincial governor and UNICEF official, was more recently in charge of running Hamyaran, an umbrella agency for Iranian nongovernmental organizations.

Support for US-Iran relations

Siamak, who has dual US citizenship, was arrested by the Islamic Revolutionary Guard Corps around October 15 while visiting relatives in Iran. Officials have yet to announce charges against him.

He was the sole US citizen who wasn't included in a prisoner exchange in January, when five Americans were freed from Iranian prisons. In return, US sentences, charges or warrants against 21 Iranians were dropped.

The businessman, who has advocated for improved diplomatic relations between the US and Iran, most recently worked for Crescent Petroleum in the United Arab Emirates, and previously headed a consulting firm in Iran.

On Wednesday, US Secretary of State John Kerry said he was aware of reports of Baquer's arrest and was "engaged" on the issue. He was unable to comment further.

ksb/cmk (Reuters, AFP, AP)