Former inmates have described being subjected to mock executions, beatings and psychological "torture" in the notorious prison where three Australians are being held.

Key points: Activists say foreigners are usually tried on the "ambiguous" charge of espionage

Activists say foreigners are usually tried on the "ambiguous" charge of espionage Previously detained foreigners say torture was mainly psychological rather than physical

Previously detained foreigners say torture was mainly psychological rather than physical Activists say it is becoming routine for Iran to detain Westerners

Perth bloggers Mark Firkin and his partner Jolie King were arrested 10 weeks ago and are now detained in Tehran's Evin prison, along with a third Australian — a female academic being held in solitary confinement who was reportedly sentenced to 10 years in prison after her arrest in October last year.

Jason Rezaian, an Iranian-American writer for the Washington Post, was detained along with his wife in 2014 when he was the paper's Tehran bureau chief. He was held for 544 days on charges of espionage.

Mr Rezaian said most of the foreigners were held in "very severe isolation away from the general prison population".

Jason Rezaian, an Iranian-American writer for the Washington Post, was detained along with his wife in 2014. ( AFP )

"Through my entire year and a half in detention I only had interactions with two other prisoners," Mr Razaian told the ABC, adding that he was mostly held in solitary confinement.

"When it first happens, your first thought is that this is a big mistake and someone will talk some sense into the people who have taken you captive.

"And then the days and weeks start to mount."

Evin prison has became synonymous with torture and death, with thousands of reported hangings, the disappearance of numerous political detainees and an "appalling level of brutality" as detailed in reports by Amnesty International.

Former detainees described walls topped with barbed wire, windowless cells, air that reeked of "sweat and vomit" and sounds of gun fire and "pain-saturated" screams.

"The pattern of arresting foreign nationals in Iran is becoming increasingly alarming," said Amnesty's Eilidh Macpherson in a statement published on the organisation's website.

"We're concerned [the three Australians] may have been subjected to serious human rights violations, including denial of access to a lawyer and even torture or other ill-treatment."

'Torture is mainly psychological rather than physical'

Space to play or pause, M to mute, left and right arrows to seek, up and down arrows for volume. Watch Duration: 1 minute 7 seconds 1 m 7 s Jolie King and Mark Firkin posted about their travels through Pakistan in June, before they were detained in Iran.

Mr Firkin and Ms King, who were reportedly arrested for flying a drone without a permit, run a YouTube channel called The Way Overland.

The detained couple posted on a crowd-funding site that they were hoping to inspire others to travel "to countries which get a bad wrap in the media".

Online followers raised concerns after the bloggers did not post for several weeks.

According to a report by The Times newspaper, Ms King was kept in isolation for weeks but has recently been moved into a communal ward of Evin prison.

A British-Iranian prisoner who met her there said Ms King was initially terrified and "very unsure of everyone" when she was moved into the communal ward.

Nazanin Zaghari-Ratcliffe said Ms King had been "scared, disoriented and intimidated" by her time in solitary confinement.

But Ms King has since become more upbeat, The Times reported, with her British cellmate quoted as saying the young traveller had "a really fun sense of humour, and is very creative at making things with her hands".

Jolie King and Mark Firkin have been travelling around the world since 2017. ( Instagram: Jolie King )

Kaveh Taheri, a human rights activist and co-founder of the Institute of Capacity Building for Human Rights, said Iran often arrests foreigners "on the basis of its needs" in dealing with the international community.

Mr Taheri, who himself was detained as a political prisoner in Iran before fleeing to Turkey, said foreigners are usually tried on "the ambiguous charge of espionage".

"This regime targets dual national citizens and foreigners, whom they perceive to have links with Western governments, organisations, or academic centres," he told the ABC.

Two of the detained Australians hold dual British and Australian citizenship.

'The world is monitoring … and the regime knows that'

The Australian travel bloggers were reportedly arrested for flying a drone without a permit. ( Instagram: Jolie King )

Mr Taheri said prison conditions, torture methods and treatment can vary greatly from prison to prison and by which security agency controls it, but most foreigners are transferred to the capital.

"The treatment against foreigners is undoubtedly different, because the regime needs to be accountable for its behaviour to the international community," he said.

"Torture is mainly psychological rather than physical."

Mr Taheri described cases where prisoners were blindfolded and made to sit on the floor in silence for hours before guards would suddenly begin "screaming vulgar sexual terms against them or their relatives".

He also described mock executions, something Mr Rezaian was also all too familiar with during his own detainment.

Mr Rezaian was one of four American prisoners released in January 2016. ( Reuters: Kai Pfaffenbach )

"At certain points I'd be told that I was about to be released within a matter of hours. On other days I'd be told I'd be executed in a matter of hours and you really never know which is true," Mr Rezaian said of his one-and-a-half-year detainment in Evin.

"Part of what they're trying to accomplish is to get you to lose hope."

But Mr Taheri offered some reassurance to the families of the three detainees.

"Do not forget it, the three Australians … are under the protection of the international community. The world is monitoring the situation, and the regime knows that," he said.

"But, prison is prison. It means they are locked up. It doesn't matter if they treat them well or poorly. They are, unfortunately, deprived of their fundamental rights."

Mr Taheri urged all Australian citizens to put "maximum pressure" on the Government to hold Iran accountable for these detentions.

'They put me in front of a firing squad'

As an Iranian political prisoner, Mr Taheri experienced phycological torture, mock executions and also beatings.

"I was not permitted to contact my family at all. I was beaten many times during which they used the vilest language to insult members of my family," he said.

Ms Nemat wrote extensively of her years in prison and it's aftermath in two books. ( Supplied )

After his initial interrogation he was transferred to a prison where he was held with violent offenders who would often threatened rape, which "the prison authorities chose to ignore".

Mr Taheri said due to a lack of heating, his health deteriorated and he contracted severe influenza for which he was denied medical care.

Author Marina Nemat, now living in Canada, was 16 when she was arrested and sent to Evin prison in 1982 "for speaking out against the government and attending protest rallies".

"My first night in Evin, they tied me to a bare wooden bed and lashed the soles of my feet with a length of cable until my feet looked like blue party balloons with toes on them," she told the ABC.

Ms Nemat wrote extensively of her years in prison and the aftermath in her books, Prisoner of Tehran and After Tehran: A Life Reclaimed.

In her books she described windowless cells, prison air that reeked of "sweat and vomit" and the sounds of piercing "pain-saturated" screams.

When she was moved around the prison, she said she was blindfolded and dragged along by a rope tied around her wrists, as screams echoed through the halls.

"They also put me in front of a firing squad and I thought they were going to kill me but they didn't," Ms Nemat told the ABC.

"I spent months in solitary confinement. Many of my friends were executed and are buried in mass graves."

Ms Nemat warned the Iranian Government "should never be underestimated".

"When Australians are arrested, it means that the Iranian Government wants something from Australia."

'Held as leverage for future political concessions'

Evin prison has become synonymous with an "appalling level of brutality" according to Amnesty International. ( Reuters: Morteza Nikoubazl )

Mr Rezaian's detention took place at the height of the nuclear negotiations between Iran and world powers.

"The group within the Iranian regime that took me hostage was one that did not want those negotiations to come to fruition," he said, adding he believed his detention was an effort to undermine the deal before it was signed.

"I think more often than not, when a foreign national is taken, it can be safely assumed that they are being held as leverage for future political concessions from their home government."

Mr Rezaian was one of four American prisoners released ahead of the Iran nuclear deal, which was to curb Tehran's nuclear program in exchange for the lifting of international sanctions on Iran.

Mr Rezaian said securing the Australians' release won't be an easy task.

"I think the best thing to do is to be as loud, vocal and consistent in calling for their release as possible," he said, warning that "concessions" would likely be needed on the part of the Australian Government to secure their release.

"I am always one to say: get that process started sooner rather than later and save these people the terror and deep trauma that is inflicted upon them.

"Because every day that you are in there is a day of suffering that no one should have to endure."

The Iranian Government and the Iranian embassy in Canberra have not yet responded to requests for comment.