Nazanin Zaghari-Ratcliffe, the British-Iranian woman detained in Tehran for more than three years, has been transferred to a mental health ward where Iran’s Revolutionary Guards have prevented relatives from contacting her, according to her husband.

Richard Ratcliffe said his wife was moved from Evin prison on Monday to the mental ward of Imam Khomeini hospital. Her father tried to visit her there but was repeatedly denied access by the guards, who also prevented him from calling his daughter, Ratcliffe said.

Her relatives expressed serious concern on Wednesday, saying it was “unusual for political prisoners to be guarded by the Iranian Revolutionary Guard Corps, rather than regular prison guards during hospital treatment”.

Zaghari-Ratcliffe was arrested at Tehran’s Imam Khomeini airport while travelling with the couple’s daughter in April 2016 and accused of spying. The Thomson Reuters Foundation employee faced charges of spreading “propaganda against the regime”.

She vehemently denied the allegation, saying she was in Iran to visit her family, and her account was backed by her employer, but she was sentenced to five years in jail in September of that year.

However, she was further imperilled when Boris Johnson, the then foreign secretary who is now frontrunner to become the next prime minister, mistakenly said she was “teaching people journalism” in Iran. While he later corrected his error, it was cited as evidence against her.

In 2016, a UN working group said it considered Zaghari-Ratcliffe to have been arbitrarily detained.

According to those campaigning for her to be freed, she said shortly before she was transferred to the ward: “I was healthy and happy when I came to Iran to see my parents. Three and a bit years later and I am admitted to a mental health clinic.

“Look at me now, I ended up in an asylum. It should be an embarrassment. Prison is getting harder and harder for me. I hate being played in the middle of a political game. I just hate it.”

The couple recently held simultaneous hunger strikes in London and Iran. On Wednesday, Richard Ratcliffe said: “Nazanin hoped that her hunger strike would move the Iranian authorities, and it clearly has.

“Hopefully, her transfer to hospital means that she is getting treatment and care, despite my distrust of just what pressures can happen behind closed doors. It is unnerving when we don’t know what is going on.”

Earlier this year, the current foreign secretary and Tory leadership hopeful, Jeremy Hunt, granted Zaghari-Ratcliffe diplomatic protection in a bid to resolve her case.

Tensions between the two countries, already heightened, have increased yet further recently. Earlier this month, Royal Marines helped seize an Iranian supertanker suspected of carrying oil to Syria off the coast of Gibraltar. Last week, three Iranian boats tried to intercept a British oil tanker in the Gulf before being driven off by a Royal Navy warship.