Four Americans imprisoned in Iran, including a journalist held as prisoner for the last 18 months, have been freed, the Washington Post reported Saturday.

Washington Post reporter Jason Rezaian , 39, had been convicted on various charges, including espionage by the Iranian government. Rezaian and the other three prisoners released hold dual citizenship in the U.S. and Iran.

ADVERTISEMENT A U.S. official confirmed to the Associated Press that the four prisoners, also including former U.S. Marine Amir Hekmati, will be freed on Saturday. The prisoners will be flown from Iran to Switzerland on a Swiss plane.

The releases come as part of a prisoner swap.

“Based on an approval of the Supreme National Security Council (SNSC) and the general interests of the Islamic Republic, four Iranian prisoners with dual-nationality were freed today within the framework of a prisoner swap deal,” a Tehran prosecutor was quoted as saying by Iran’s Fars news agency. The Associated Press reported that the U.S. freed seven Iranian-Americans held on sanctions related charges. The imprisonment of the four Americans, particularly Rezaian, had drawn growing outrage in the United States. American journalists held events to draw attention to his plight. Republicans criticized the Obama administration for striking a nuclear deal without obtaining the release of the Americans. Hekmati, the former Marine, was imprisoned weeks after arriving in Iran to visit his grandmother in 2011. He was accused of spying and confessed on television. A letter from Hekmati said the confession was coerced. Another prisoner released is Saeed Abedini, an Iranian native who later converted to Christianity, becoming a pastor and settling in Idaho. He has been held for three years, accused of undermining national security. CNN reported the fourth prisoner being released as Nosratollah Khosrawi. Details were not immediately known.

The news came as world leaders are gathering in Vienna, Austria, in preparation for the lifting of some sanctions on Iran after the International Atomic Energy Association certifies that Iran has met its commitments under the nuclear deal.

State Department spokesman John Kirby said last week that the department was “working very hard to get our citizens back home and we call again on Iran to release them.”

- Updated at 12:06 p.m.