Rezaian, 39, was convicted of espionage in Iran last year.

Iranian state TV named the other three as Saeed Abedini, Amir Hekmati and and Nosratollah Khosravi.

Iran said they were being swapped for seven Iranians held in US prisons but there was no immediate US confirmation.

The Iranian state news agency listed the seven as Nader Modanlo, Bahram Mechanic, Khosrow Afghani, Arash Ghahreman, Tooraj Faridi, Nima Golestaneh and Ali Saboun.

In addition, Iranian state TV said 14 Iranians sought by the US would be removed from an Interpol wanted list.

News of the releases came after Iranian Foreign Minister Javad Zarif predicted that international sanctions against his country would be lifted on Saturday.

He is in Vienna for talks with US Secretary of State John Kerry over Iran`s nuclear deal.

The international nuclear watchdog, the IAEA, is expected to confirm that Iran has scaled back its atomic activities in line with the agreement.

Billions of dollars of frozen Iranian assets are expected to be released and the sale of Iranian oil on the world market will again be permitted.

Lifting sanctions would unfreeze billions of dollars of assets and allow Iranian oil to be sold internationally.

Jason Rezaian, the Washington Post`s Tehran correspondent, had been detained in Iran for more than a year before his sentencing last November. The WP has dismissed the charges as absurd.

The other three freed on Saturday were: Saeed Abedini, 35, a Christian pastor who had been imprisoned since July 2012 for organising churches in people`s houses; Amir Hekmati, 32, a former Marine who spent more than four years in prison on spying charges following his arrest in August 2011 during a visit to see his grandmother. The detention of Khosrawi had not been previously released.

The Associated Press news agency had named the fourth prisoner known to be held in Iran as Siamak Namazi, a businessman and the son of a politician from the shah`s era.

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