The New York-based International Campaign for Human Rights in Iran said Friday that Karan Vafadari and his Iranian wife Afarin Niasari are being held in Tehran's Evin Prison.
The group says no public charges have been brought and the couple has not had access to a lawyer since their arrest by the Revolutionary Guard in July.
Iranian officials could not immediately be reached for comment.
Iran does not recognize dual nationality. Several dual nationals arrested in recent years have faced secret charges in closed-door hearings, including Washington Post journalist Jason Rezaian, who was released in January.
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