Much of the country has seen protests following the death of a young woman in custody. Photo: Anadolu Agency via AFP
Iran's president has vowed to take action against protesters after more than a week of anti-government demonstrations.
President Ebrahim Raisi pledged to "deal decisively" with the protests, which have now spread to most of Iran's 31 provinces.
Officials say some 35 people have been killed since protests broke out over the death of a woman in police custody.
Mahsa Amini died after being detained for allegedly breaking headscarf rules.
Mahsa Amini died after being arrested and detained by the morality police in Tehran. Photo: Supplied
Officers reportedly beat Amini's head with a baton and banged her head against one of their vehicles. The police have said there is no evidence of any mistreatment and that she suffered "sudden heart failure".
And while Raisi says her death will be investigated, his Interior Minister Ahmad Vahidi has insisted that Amini had not been beaten.
"Reports from oversight bodies were received, witnesses were interviewed, videos were reviewed, forensic opinions were obtained and it was found that there had been no beating," he said.
Videos circulating on social media have captured violent unrest in dozens of cities across the country, with some showing security forces firing what appeared to be live ammunition on protesters in the north-western cities of Piranshahr, Mahabad and Urmia.
Amnesty International has warned that evidence it gathered pointed to "a harrowing pattern of Iranian security forces deliberately and unlawfully firing live ammunition at protesters".
It added that government forces shot 19 people dead - including three children - on Wednesday night alone. The BBC cannot independently verify this.
Raisi has dismissed the protests as "riots". Iran, he said, must "deal decisively with those who oppose the country's security and tranquillity".
A demonstration to protest the death of Mahsa Amini in Tehran on 21 September. Photo: ANDALOU
Hundreds of people have been detained by security forces, with the police chief in the north-western province of Guilan announcing on Saturday that some 739 people - including 60 women - have been detained in his region alone.
The BBC has heard testimony from some of those arrested who allege they were beaten. One said he was beaten "ruthlessly" before being jailed in a small cell with hundreds of others, where they were deprived of food, water and access to a bathroom.
Government forces have also launched a crackdown on independent media and activists. The US-based media watchdog the Committee to Protect Journalists says 11 journalists have been detained since Monday.
In the western border town of Oshnavieh, sources told the BBC that demonstrators briefly took control of sections of the town from government forces.
Locals told the BBC that demonstrators had seized control overnight and that security forces and government officials had fled, before regaining control on Saturday. Videos posted from the town showed large crowds of people marching through city streets with no police presence, while loud explosions could be heard.
State media denied the reports, but said protesters had stormed three outposts of the Basji Organisation, a paramilitary associated with the government's Revolutionary Guards.
The US says it will ease internet curbs on Iran to counter Tehran's clampdown on the protests, with Secretary of State Antony Blinken pledging to "help make sure the Iranian people are not kept isolated and in the dark".
- BBC