The plight of British-Iranian woman Nazanin Zaghari-Ratcliffe, sentenced to five years in jail after being convicted of spying, has focused attention on Iranians with dual nationality or foreign permanent residency who are held in the Islamic Republic's prisons.
Iran does not recognise dual nationality, and there are no exact figures on the number of such detainees given the sensitive nature of the information. Beside Ms Zaghari-Ratcliffe, some of the most prominent are:
Siamak and Baquer Namazi (Iran-US)
Siamak Namazi worked as head of strategic planning at Dubai-based Crescent Petroleum.
He was arrested by the Revolutionary Guards in October 2015, while his octogenarian father Baquer was arrested in February 2016 after Iranian officials granted him permission to visit his sonin prison.
That October, they were both sentenced to 10 years in prison by a Revolutionary Court for "co-operating with a foreign enemy state". An appeals court upheld their sentence in August 2017.
Their lawyer said they denied the charges against them. He also complained that they had been held in solitary confinement and denied access to legal representation, and had suffered health problems. Siamak is also alleged to have been tortured.
The UN Working Group on Arbitrary Detention said the Namazis' imprisonment violated the Universal Declaration of Human Rights and the International Covenant on Civil and Political Rights, and demanded their release.
In March 2018, Baquer was given medical leave from prison and placed under house arrest. The Namazi family has warned that his health was rapidly deteriorating.
Ahmadreza Djalali (Iran-Sweden)
The specialist in emergency medicine was arrested in April 2016 while on a business trip from Sweden.
Amnesty International said Djalali was held at Evin prison by intelligence ministry officials for seven months, three of them in solitary confinement, before he was given access to a lawyer.
He alleged that he was subjected to torture and other ill-treatment during that period, including threats to kill or otherwise harm his children, who live in Sweden, and his mother, who lives in Iran.
In October 2017, a Revolutionary Court in Tehran convicted Djalali of "spreading corruption on earth" and sentenced him to death. His lawyers said the court relied primarily on evidence obtained under duress and alleged that he was prosecuted solely because of his refusal to use his academic ties in European institutions to spy for Iran.
Two months later, Iranian state television also aired what it said was footage of Djalali confessing that he had spied on Iran's nuclear programme for Israel. It suggested he was responsible for identifying two Iranian nuclear scientists who were killed in bomb attacks in 2010.
In November 2020, Iran dismissed an appeal by Sweden's foreign minister for it to not enforce the death sentence, after Djalali's wife said he had been informed by prison authorities that faced imminent execution.
Sweden gave Djalali citizenship in 2018. He had previously been a permanent resident.
Abdolrasoul Dorri Esfahani (Iran-Canada)
The accountant was an adviser to the governor of Iran's central bank and was a member of the Iranian negotiating team for the country's 2015 nuclear deal with world powers, in charge of financial issues.
He was arrested by the Revolutionary Guards in August 2016 just before he was due to board a flight to Canada, and was accused of "selling the country's economic details to foreigners".
In May 2017, a Revolutionary Court in Tehran convicted Dorri Esfahani on espionage charges, including "collaborating with the British secret service", and sentenced him to five years in prison.
That October an appeals court upheld Dorri Esfahani's sentence, despite Intelligence Minister Mahmoud Alavi insisting that he was innocent.
Dorri Esfahani's status and location was unknown as of late 2020, according to the Center for Human Rights in Iran, a New York-based advocacy group.
Morad Tahbaz (Iran-UK-US)
The businessman and wildlife conservationist, who also holds American and British citizenship, was arrested during a crackdown on environmental activists in January 2018. His Canadian-Iranian colleague, Kavous Seyed-Emami, died in custody a few weeks later in unexplained circumstances.
The authorities accused Tahbaz and seven other conservationists of collecting classified information about Iran's strategic areas under the pretext of carrying out environmental and scientific projects.
The conservationists - members of the Persian Wildlife Heritage Foundation - had been using cameras to track endangered species including the Asiatic cheetah and Persian leopard, according to Amnesty International.
UN human rights experts said it was "hard to fathom how working to preserve the Iranian flora and fauna can possibly be linked to conducting espionage against Iranian interests", while a government committee concluded that there was no evidence to suggest they were spies.
But in October 2018, Tahbaz and three of his fellow conservationists were charged with "corruption on earth" (later changed to "co-operating with the hostile state of the US"), which carries the death penalty. Three others were charged with espionage, and a fourth was accused of acting against national security.
All eight denied the charges and Amnesty International said there was evidence that they had been subjected to torture in order to extract forced "confessions".
They were sentenced to prison terms ranging from four to 10 years and ordered to return allegedly "illicit income".
Human Rights Watch denounced what it said was an unfair trial, during which the defendants were apparently unable to see the full dossier of evidence against them.
Kamran Ghaderi (Iran-Austria)
The CEO of Austria-based IT management and consulting company Avanoc was detained during a business trip to Iran in January 2016.
That October, an Iranian prosecutor said Ghaderi had been sentenced to 10 years in prison after being convicted of espionage and co-operating with a hostile state.
His wife insisted that he was a "simple businessman" who was unjustly imprisoned, while human rights groups said he was coerced into confessing to spying.
Ghaderi's physical and mental health has deteriorated in prison. In July 2019, UN human rights experts said he had been denied appropriate medical treatment, despite having a tumour in his leg.
Karan Vafadari and Afarin Neyssari (Iran-US)
The couple, who are Zoroastrians, own a well-known art gallery. They were arrested by the Revolutionary Guards at Tehran's international airport in July 2016.
Two weeks later, the Tehran prosecutor announced that "two Iranian dual nationals" had been charged with hosting parties for foreign diplomats and Iranian associates during which men and women mixed and alcohol was served.
Iran's constitution says adherents of Zoroastrianism - an ancient, pre-Islamic religion - are not subject to Islamic laws on alcohol and mixed gender gatherings.
In early 2017, further charges were brought against Vafadari and his wife, including "co-operation with enemies of the state", "activities to overthrow the regime" and "recruitment of spies through foreign embassies".
In January 2018, Vafadari wrote in a letter from Evin prison saying that a Revolutionary Court had sentenced him to 27 years in jail and his wife to 16 years, according to the US-based Center for Human Rights in Iran (CHRI). He vigorously rejected all the charges they faced.
The couple's sentences were later reduced to 15 years and 10 years respectively, their son said.
In July 2018, the authorities reportedly released them on bail, pending an appeal.
Fariba Adelkhah (Iran-France)
The researcher at Sciences Po university in Paris is a specialist in social anthropology and the political anthropology of post-revolutionary Iran, and has written a number of books.
At the time of her arrest in Tehran in June 2019, she was examining the movement of Shia clerics between Afghanistan, Iran, and Iraq, and had spent time in the holy city of Qom.
Adelkhah was accused of espionage and other security-related offences.
She protested her innocence and after going on hunger strike she was admitted to hospital for treatment for severe kidney damage.
Prosecutors dropped the espionage charge before her trial began at the Revolutionary Court in April 2020. The following month, the court sentenced Adelkhah to five years in prison for conspiring against national security and an additional year for propaganda against the establishment.
French Foreign Minister Jean-Yves Le Drian condemned the sentence and demanded her release.
In October 2020, due to what Sciences Po called her "health circumstances", Adelkhah was released on bail and and returned to her home in Tehran, where she remains under house arrest.
Anoosheh Ashoori (Iran-UK)
The retired British-Iranian civil engineer was arrested in August 2017 during a visit to Tehran.
According to his family, he was held in solitary confinement during his first six weeks of detention, interrogated without access to a lawyer and taunted with threats to his family.
Ashoori said he was forced to sign "confessions" under torture and other ill-treatment, including sleep deprivation and prolonged solitary confinement.
At trial, where he represented himself after being denied the right to appoint a lawyer of his choosing, Ashoori retracted his alleged "confessions". However, the court failed to order investigations and used the statements to convict him, according to Amnesty International.
In August 2019, the spokesman for Iran's judiciary announced that Ashoori had been sentenced to 10 years in prison for spying for Israel, as well as two years for "illicitly acquiring money" and fined $36,600.
Ashoori's wife, Sherry Izadi, said the claims were "preposterous" and asked the UK government to help free him.
Kameel Ahmady (Iran-UK)
Mr Ahmady, who is an ethnic Kurd, was born in north-western Iran and moved to the UK in his 20s, studying at the London School of Economics.
In 2015, he published a study suggesting that tens of thousands of Iranian women had undergone female genital mutilation. Until then, Iran had not been widely recognised as a country affected by FGM.
Mr Ahmady had been living in Iran for several years before his arrest in August 2019, according to the Kurdistan Human Rights Network, a France-based advocacy group.
The academic said he spent 100 days without access to a lawyer before he was allowed out on bail.
In December 2020, Mr Ahmady's lawyer said he had been sentenced by a Revolutionary Court in Tehran to eight years in prison after being convicted of "collaborating with a hostile government".
Mr Ahmady wrote on Facebook that the judgement followed a "legal process full of flaws" and that he would appeal.
Massud Mossaheb (Iran-Austria)
The former businessman, who is an Austrian-Iranian dual national, was arrested in Tehran in January 2019.
Amnesty International cited informed sources as saying Mossaheb was held in a hotel room for three days, where intelligence ministry agents subjected him to torture through sleep deprivation, interrogated him without a lawyer present, and coerced him into signing documents.
He was then transferred to Evin prison, where according to the sources he was tortured.
In April 2020, Mossaheb was sentenced to 22 years in prison after being convicted of "espionage for Germany", "collaborating with a hostile government" - a reference to Israel - and "receiving illicit funds" from both countries.
Amnesty International said the trial was "grossly unfair", with the court relying on relying on alleged "confessions" that he retracted in court and told the judge he had made under torture.
In November, the human rights group warned that Mossaheb's health was declining and that his life might be at risk.
Nahid Taghavi (Iran-Germany)
The retired architect, a German-Iranian dual national, was arrested at her apartment in Tehran in October 2020 and accused of "endangering security".
She has been placed in solitary confinement at Evin prison and not given access to lawyers, German diplomats or members of her family, according to her daughter Mariam Claren. She was not allowed to make a telephone call for 12 days.
Ms Claren has said she is concerned that her mother is being denied medical care. She was arrested two days after undergoing dental surgery and has a history of high blood pressure.