Prisoner captive jail bars
Prisoner captive jail barsThinkstock

Four American citizens imprisoned by Iran have been released Saturday in a prisoner exchange with the United States.

US officials confirmed reports published earlier Saturday that Washington Post journalist Jason Rezaian, Marine veteran Amir Hekmati, Christian pastor Saeed Abedini, and Nosratollah Khosrawi have all been freed by the Islamic regime.

The prisoner swap, which will also see seven Iranians jailed in America for violating sanctions against Iran, was the culmination of 14 months of secret negotiations.

A fifth American citizen, Matthew Trevithick, has also been released by Tehran - though Iranian officials say his release was unconnected to the prisoner swap.

It comes on the same day as the UN's International Atomic Energy Agency (IAEA) is expected to announce that Iran is in compliance with its side of the nuclear deal reached with world powers in July last year, enabling the first batch of sanctions relief to Tehran.

The US citizens were still in Iran as of 11:15 ET, according to CNN, but are expected to fly back to the US imminently.

All of those released by Iran were dual Iranian-American citizens.

Rezaia and Hekmati were jailed on charges relating to alleged "espionage," which human rights groups, friends and family dismissed as trumped-up, politically-motivated charges.

Abedini was accused of missionary activity - which is often punishable by death in the Islamic Republic - but was jailed for eight years for the lesser, vague crime of "undermining the government".

The circumstances behind Khosrawi's detention are not clear.

The deal did not address the disappearance of another American citizen, Robert Levinson, who is believed to be held by the Iranian regime.