Iran has arrested a Lebanese-American on suspicion of having links to the American intelligence community, AFP reported Tuesday, citing Iranian state television.
An official in Washington indicated the man was not a U.S. national, however.
It was unclear when or where the suspect had been arrested but the Iranian report identified him as Nezar Zaka and said he was suspected of "multiple close ties to the U.S. military and intelligence communities."
The broadcaster aired photographs of what it said was Zaka in military uniform on an American base, according to AFP.
But the State Department, while not officially confirming there had been an arrest, said the suspect was Lebanese with permanent American residency papers.
Elizabeth Trudeau, a State Department spokeswoman quoted by the news agency, said the man had a "green card" rather than a U.S. passport, so it was up to his country of origin to provide consular service.
Iran is currently holding four Iranian-Americans in custody, including Washington Post correspondent Jason Rezaian, who has been held since July last year on spy charges, and in whose case a verdict was recently reached.
Iranian officials have not detailed the charges of which he has been convicted but have said that he can appeal.
Iran’s Foreign Minister Mohammad Javad Zarif has said the country is trying to resolve Rezaian's case "from a humanitarian point of view."
Two other Americans in Iranian custody are Amir Hekmati, a former American Marine who was charged with spying, and Saeed Abedini, a convert to Christianity who gathered a Bible study group.
Hekmati, who was arrested in 2011, was put on trial and found guilty of spying for the CIA. He was subsequently sentenced to death, a penalty that was eventually overturned and reduced to 10 years in prison.
The United States has regularly demanded the unconditional release of the three prisoners. Tehran does not recognize dual nationality for its citizens.