A Kenilworth woman whose sister was arrested in her home in Iran in the middle of the night has described her situation as "a nightmare nobody wants to wake up to".

Nessa Armstrong has told how her sister Sara Fereshteh was taken by police from her flat in Tehran in the middle of the night on September 25.

Protests that have swept across Iran over the past few weeks following the death of a young woman in custody who was arrested for allegedly breaking rules requiring women to cover their hair with a hijab.

Police said Mahsa Amini, 22, collapsed at a detention centre after suffering heart failure, but her family have claimed she was beaten by officers.

Following Ms Amini's funeral on September 17 protests have reached more than 80 cities and towns across the country and state media has reported that more than 1,400 people have already been arrested.

But Sara, an artist who also worked at the French Embassy, still does not know why she has been arrested.

As the protests continued, she had made sure to regularly let her family in England know that she was safe.

However, sister Nessa said all of a sudden, she was no longer able to contact her.

"I tried to call her and I couldn't reach her so I phoned my cousin again and she didn't know anything," Nessa told Nub News. 

"Then the day after my other cousin, who lives with my sister, said that Sara had been arrested. 

"They basically broke in in the middle of the night, smashed down one of the doors and took all of my cousin's belongings."

She added: "They have taken her without giving her any rights to call or tell anyone, if they had taken my cousin as well then we wouldn't know what had happened to them."

Sara Fereshteh has still not been told what she has been charged with (image supplied)

Two days after Sara was arrested she was allowed a brief call to her father from prison, but still did not know where she had been taken to.

Eventually she was able to tell her family that she had been taken to the notorious Evin Prison but had still not been told what her charges were.

"It's a nightmare that nobody wants to wake up to," Nessa said. 

"We don't know when they will get out, or how long it is going to be because they can put anything as a charge from treason, being against the Islamic Republic of Iran, it can be anything."

Nessa said the situation was "even worse now" because her mother had flown from England to Iran to have someone "standing up for Sara" there.

A researcher at the University of Warwick, Nessa said she had already received a lot of support from people in Kenilworth.

"Everyone has been very supportive," she said. 

"I am a member of a local mum's group and they have all written to our MP about it, and he has written to me saying that he has escalated it."

She added: "I don't know what can be done because she is not British. 

"It is different to Nazanin's [Zaghari-Ratcliffe] case. Obviously there was a lot more effort for Nazanin but she was a citizen. 

"But it's human rights so I don't think it should matter where you are from. But I guess their hands are tied."

President Ebrahim Raisi told state TV last month that Ms Amini's death was being investigated but said there was a "distinction between protests and riots".

"Those who took part in the riots must be dealt with decisively, this is the demand of the people," he added.

But Nessa said: "Prison should be a place for criminals, this is a great injustice. 

"Nobody as normal as my sister should be in the situation that she is in now. She is not an activist. 

"This is not something that should have happened to her or the people who are being shot in Iran right now just because they are fighting for their human rights."