A Dubai-based businessman has become the fourth Iranian-American to be arrested by Iran's security forces and imprisoned in Tehran, Tehran begins implementing a nuclear deal struck with world powers, several US newspapers reported.

The detention of Siamak Namazi, believed to be in his early 40s, comes as an Internet freedom group said a Washington-based Lebanese citizen recently disappeared while on a trip to Tehran, the New York Times reported.

Iranian officials and state media have yet to comment on either case, though there's speculation that some in Iran want to negotiate a prisoner swap with the US for others held in Iran, like detained Washington Post reporter Jason Rezaian.

Namazi was arrested earlier this month while visiting a friend in Tehran, a family friend told The Washington Post. It was not immediately clear whether any charges have been brought against Namazi. The friend asked not to be identified.

The US State Department declined to confirm Namazi's arrest.

"We're aware of recent reports of the possible arrest in Iran of a U.S. citizen. We're looking into these reports and don't have anything further to provide at this time," Michael Tran, a State Department spokesman, said.

Namazi, the son of a former governor in the oil-rich Iranian province of Khuzestan, comes from a prominent Iranian family, which came to the United States in 1983 when he was a boy, according to The Washington Post.

Namazi's arrest — also reported by The New York Times and The Wall Street Journal — suggests that hard-liners in Iran could be trying to create tension with the United States in the wake of Iran's nuclear deal with world powers. That agreement reached earlier this year promises Iran relief from crippling economic sanctions in exchange for curbs on its nuclear program.