By Alex Binley & Elsa Maishman
A major fire has broken out at Iran’s notorious Evin prison, known for housing political prisoners, journalists and foreign nationals.
Videos shared online show flames and smoke at the site in Tehran, and gunshots and explosions can be heard.
An official quoted by state media said the situation was under control, but video footage appeared to show the fire continuing after this.
Iran has been gripped for weeks by anti-government protests.
They first erupted last month after the death of 22-year-old Kurdish Iranian Mahsa Amini in police custody. Officials said she died of a heart attack, but her family disputed this, saying she was beaten by morality police.
BBC Persian’s Rana Rahimpour said it is not yet known whether the situation at the prison is linked to the recent demonstrations.
But this could easily be the case, Rana said, as hundreds of the protesters have been sent to Evin.
State media has suggested the two are not linked, quoting an official who blamed “criminal elements” for the fire.
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In a video posted on social media by anti-government monitoring group 1500tasvir, chants of “death to the dictator” – one of the main slogans of the anti-government protest movement – could be heard coming from outside the prison.
Another video appears to show objects being fired into the prison from outside its perimeter, and an explosion is then heard, according to BBC Persian.
Iranian media, which is strictly controlled by the government, reported that the riot started with financial and criminal prisoners, and that no political prisoners were involved. Eight people had been injured, it said.
Speaking from inside the prison, Tehran’s governor told state TV that the riot was in a wing of the prison housing petty criminals and the situation was now completely calm.
However, the situation at the prison is still confused, reports BBC Persian’s Kasra Naji. Videos continue to be posted on social media showing the fire still burning and the sound of gunfire heard around the prison.
Other pictures show inmates on the roof of a section of the prison where political prisoners and many of the protestors who have been arrested in the past four weeks are kept, Kasra said.
The families of some prisoners told the BBC that they were unable to contact their relatives on the phone, and that internet connection around the prison also appeared to have been cut off.
The streets leading to the prison were closed.
Earlier, videos showed riot police entering Evin. There were also reports that special forces had been deployed to the area. A witness told Reuters news agency that ambulances were also there.
Nazanin Zaghari-Ratcliffe, a dual citizen of both the United Kingdom and Iran, and Anoosheh Ashoori were both detained at the Evin prison for a number of years on suspicion of spying before being freed earlier this year.
The prison has long come under fire from Western human rights organizations. Human Rights Watch has charged the prison’s administrators with using torture threats and indefinite detention as well as protracted interrogations and denying inmates medical care.
In August of last year, a group of hackers going by the name Edalat-e Ali (Ali’s Justice) posted videos of leaked surveillance footage from the Evin prison showing guards abusing or beating inmates.
Some foreign governments whose citizens are being held in the prison have expressed concern.
A spokesperson for the US state department said it was following events with “urgency”, while the UK Government’s security minister called it a “very worrying development”.
Since the death of Ms Amini five weeks ago, a wave of protests has swept across Iran in the boldest challenge to the Islamic Republic since its establishment in 1979.
Many of those who have died have been teenagers.
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