An Iranian-American businessman was arrested by Iranian security forces two weeks ago while he was visiting relatives in Tehran from his home base in Dubai, the Wall Street Journal has reported.
The newspaper, citing people briefed on the situation, said on Thursday that Siamak Namazi, head of strategic planning at Crescent Petroleum Co, was arrested by the Revolutionary Guard's intelligence arm, which reports to Supreme Leader Ayatollah Ali Khamenei.
The Washington Post reported the same information about the arrest on Thursday, citing family sources.
In recent weeks, Iranian business officials with ties to foreign companies had been held, interrogated and warned against wading into economic monopolies controlled by the Revolutionary Guard Corps, the Journal reported, quoting several businessmen interviewed inside and outside Iran.
A senior official in the US President Barack Obama's administration told Reuters: "We're aware of recent reports of the possible arrest in Iran of a US citizen. We're looking into these reports and don't have anything further to provide at this time."
The report comes as Washington has urged Tehran to free three other Americans it is holding, including Washington Post reporter Jason Rezaian and to help find Robert Levinson, an American who disappeared in Iran eight years ago.
Despite Washington's long-standing contentious relationship with Tehran, the US and other major powers forged a deal in July with Iran to curb its nuclear programme in return for relief from sanctions.
Friends of Namazi told the newspaper that his family home was ransacked by Iranian intelligence agents, who confiscated his computer and had since conducted cyber attacks on some of his email contacts.
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Namazi has been living in recent years in Dubai while working for Crescent Petroleum, sources familiar with his situation told the Journal.
He went to Tehran three months ago to visit relatives.
Namazi's friends said Iranian security agents confiscated his Iranian passport and prevented him from leaving the country, the Journal reported. They said he was being held in Tehran's Evin prison, which is where political opponents of the government are kept.
The Journal said Namazi had strongly supported the nuclear accord with Tehran and the lifting of international sanctions, which he had argued disproportionately hurt average Iranians.