British-Iranians Nazanin Zaghari-Ratcliffe and Anoosheh Ashoori were returning to Britain via Oman.

Morad Tahbaz, who has American, British and Iranian nationality, has meanwhile been released from prison on furlough to his Tehran home but still cannot leave the country.

However, the families of those who remain behind bars, under house arrest or unable to leave Iran now face an agonising wait to see if a possible deal on the Iranian nuclear programme will help the prospects of their loved ones.

Rights groups say the Western nationals held are victims of a policy of hostage-taking to force concessions from foreign powers.

Tehran insists all have been subject to proper judicial process, but supporters say they are innocent.

AFP looks at the cases that have been made public. Activists fear there may be more such cases yet to be confirmed.

- United States -

- Iranian-American businessman Siamak Namazi has been in prison since his arrest in October 2015. His father Mohammad Baquer Namazi, a former UNICEF official, was arrested in February 2016 when he went to Iran to try to free his son.

They were both sentenced to 10 years on spying charges in October 2016. Baquer, 85, had his sentence commuted in 2020 but is banned from leaving Iran and was refused permission to leave the country for surgery in October.

- Iranian-American venture capitalist Emad Sharqi was sentenced to 10 years in prison on spying charges, Iranian media reported in 2021, saying he was detained trying to flee the country.

- Britain -

- Morad Tahbaz, an Iranian-American who also holds British nationality, was arrested alongside other environmentalists in January 2018 and sentenced to 10 years in jail for "conspiring with America". He has now been released from jail to apparent house arrest.

- British-Iranian labour rights activist Mehran Raoof was arrested in October 2020 and sentenced to 10 years and eight months in prison in August 2021 on charges of disrupting national security, according to Amnesty International. There is no indication his status has changed.

- Germany -

- German-Iranian Nahid Taghavi, 67, was sentenced to 10 years and eight months in jail in August 2021 after being arrested at her Tehran apartment in October 2020.

- Jamshid Sharmahd, 66, an Iranian-German dissident, has been held by Iran since August 2020 when he disappeared while in the UAE. His family say he was forcibly transferred to Tehran, where last month he was put on trial on charges that risk the death penalty.

- France -

- French-Iranian academic Fariba Adelkhah was detained in June 2019 and in May 2020 sentenced to five years in prison on national security charges.

In October, she was moved to house arrest but jailed again in January for allegedly breaching movement rules. She has now been held for over 1,000 days.

- Tourist Benjamin Briere, 36, was arrested in Iran in May 2020, allegedly while flying a drone and taking photographs in a prohibited area.

Briere, the only Westerner held who is not of Iranian origin, was jailed for eight years on spying charges in January in a trial denounced by his family.

- Austria -

- Iranian-Austrian Massud Mossaheb, 74, was detained in January 2019 and jailed for 10 years on charges of spying for Israel and Germany.

- Iranian-Austrian businessman Kamran Ghaderi, 56, was arrested in January 2016 and sentenced for working with hostile states to 10 years in jail after a trial Amnesty called "grossly unfair".

- Sweden -

- Iranian academic Ahmadreza Djalali, a resident of Sweden, was arrested during a visit to Iran in April 2016 and sentenced to death in 2017 on charges of spying for Israel's Mossad.

He was granted Swedish citizenship while in jail. His hanging was postponed but his family says he remains on death row.

- Habib Chaab, an Iranian-Swedish dissident, disappeared during a visit to Turkey in October 2020, turning up in Iran accused of being a leading figure in an Arab separatist group and of perpetrating bomb attacks. He went on trial in January and could face the death penalty.