Iranian President Ebrahim Raisi has said authorities will take action against protesters after more than a week of anti-government demonstrations that erupted to condemn the death of a young woman after she was arrested by the "morality police."
Raisi vowed to "deal firmly" with the protests, which have now spread to most of Iran's 31 provinces.
The security authorities said that more than 700 people who participated in the protests were arrested.
Officials say around 35 people have been killed since protests erupted over the death of a woman in police custody.Mahsa Amini died after her arrest, claiming she did not abide by the rules of hijab.
There were reports that an officer hit Amini's head with a baton and slammed her head into a security vehicle. The police said there was no evidence of any mistreatment and that Amini had suffered from "sudden heart failure".
Raisi pledged to investigate Amini's death, and Interior Minister Ahmed Wahidi confirmed that Amini had not been beaten.
"We studied reports from regulatory bodies, interrogated witnesses, reviewed video clips, and forensic medical opinions, and it turned out that there was no beating," the minister said.
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Videos circulated on social media showed violent unrest in dozens of cities across the country, some of which showed security forces firing what appeared to be live ammunition at protesters in the northwestern cities of Piranshahr, Mahabad and Urmia.
Amnesty International warned that the evidence it collected points to a "horrific pattern of intentionally and unlawfully firing live ammunition at protesters by Iranian security forces".
She added that government forces shot dead 19 people, including three children, on Wednesday night alone. The BBC could not independently verify this.
Raisi condemned the protests as "riots". He said Iran should "deal firmly with those who oppose the country's security and tranquility".
Security forces have arrested hundreds of people, with the police chief of northwestern Gilan province on Saturday that some 739 people, including 60 women, have been arrested in his district alone.
Government forces also launched a campaign against activists and independent media professionals. The US-based Committee to Protect Journalists says 11 journalists have been arrested since Monday.
In the western border town of Oshenfieh, sources told the BBC that protesters briefly took control of parts of the town from government forces.
Local residents told the BBC that protesters had taken control of the area overnight and that security forces and government officials had fled before.