Evin prison fire: Gun shots and sirens heard at Iran’s notorious detention centre
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...