A British woman has been locked up in a notorious jail in Iran – for trying to watch a men's volleyball match.

Ghoncheh Ghavami, 25, was arrested and taken to Tehran's Evin jail a few days after attempting to watch a volleyball match between Iran and Italy on June 20.

She has spent 41 days in solitary confinement, according to her family.

Ms Ghavami went to the Azadi Stadium – which ironically means 'freedom' - with other women to protest against Iran's stricture, introduced after the 1979 Islamic Revolution, forbidding females to attend male sporting events.

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Harsh: Ghoncheh Ghavami, 25, was arrested and taken to Tehran's Evin jail a few days after attempting to watch a volleyball match between Iran and Italy on June 20

Detained: Ms Ghavami was arrested after trying to watch a men's volleyball match at the Azadi Stadium in Tehran (pictured)

At first Ms Ghavami, who is studying law in London, was arrested then released, but when she went back to fetch her belongings, she was re-arrested and jailed.

Several others involved in the demonstration were also detained.

Her brother, 28-year-old Iman Ghavami, told ITV News: '[The family] can barely hold themselves together.

'They are torn apart – not just my parents but my grandparents, my uncles, everybody.'

Iran's head of police, Esmail Ahmadi Moghadam, told the Fars news agency: 'In the current conditions, the mixing of men and women in stadiums is not in the public interest.

Protest: Social media campaigns have sprung up in a bid to pressurise Iran into releasing Ms Ghavami

Notorious: Ms Ghavami has spent 41 days in solitary confinement in Tehran's Evin prison (pictured)

'The stance taken by religious scholars and the supreme leader remains unchanged, and as the enforcer of law, we cannot allow women to enter stadiums.'

Social media campaigns have sprung up in a bid to pressurise Iran into releasing Ms Ghavami. There's a Facebook group dedicated to helping her and the hashtag #FreeGhonchehGhavami is being appended to Twitter posts about her plight.

The Foreign Office said it was aware of the situation, but has little sway over Iran as it does not have official diplomatic ties with it, so it's unlikely to be able to help Ms Ghavami.

Amnesty International UK spokesperson Neil Durkin told MailOnline: 'We're extremely worried about Ghoncheh's predicament.

'She's been held in solitary for over a month in Tehran's notorious Evin Prison where she's been under the control of the country's Revolutionary Guards.

'Her lawyer has had no access to her or any documents about why she's being held, though we understand she's being investigated with a view to charging her with the extremely vague offence of "propaganda against the state".

'Ghoncheh is a prisoner of conscience and should be released immediately.'