Jason Rezaian, the Washington Post's Tehran correspondent, Saeed Abedini, a Christian pastor, former US Marine Amir Hekmati, and Nosratollah Khosravi, departed ‘on a special Swiss plane’, the report said.
Iran announced their release on Saturday, just hours before Tehran's historic nuclear deal with world powers was implemented, in exchange for Washington pardoning seven Iranians accused of sanctions-busting.
State television said the seven Iranians -- Nader Modanlou, Baharam Mechanic, Khosrow Afghahi, Arash Ghahreman, Tooraj Faridi, Nima Golestaneh, and Ali Saboonchi -- ‘will be freed today’.
A fifth American was also released in a separate process, a US official has said.
Iran's ambassador to the United Nations, Gholam Ali Khoshroo, said on Saturday that Switzerland played a ‘positive role’ in the prisoner swap.
The UN nuclear watchdog announced late Saturday that Iran had complied with its side of the July 2015 accord, allowing the lifting of sanctions.