Iranian officials say they have made over 1,200 arrests — including activists, lawyers and journalists — while Fars news agency says "around 60" people have been killed in the unrest.
Iran's police have warned they will confront "with all their might" women-led protests that erupted nearly two weeks ago over the death of Mahsa Amini in custody, despite growing calls for restraint.
"Today, the enemies of the Islamic Republic of Iran and some rioters seek to disrupt the order, security and comfort of the nation using any pretext," the police command said on Wednesday, quoted by Fars news agency.
"Police officers will oppose with all their might the conspiracies of counter-revolutionaries and hostile elements, and deal firmly with those who disrupt public order and security anywhere in the country."
The statement came only hours after the UN said its secretary general, Antonio Guterres, had called on Iran's President Ebrahim Raisi not to use "disproportionate force" against protesters.
In a meeting during last week's UN General Assembly, Guterres "stressed to President Raisi the need to respect human rights, including freedom of expression, peaceful assembly and association," the UN chief's spokesperson said.
"We are increasingly concerned about reports of rising fatalities, including women and children, related to the protests," the spokesman Stephane Dujarric said.
Dozens of people have been killed since demonstrations erupted after the 22-year-old woman died following her arrest in Tehran for allegedly breaching Iran's rules on hijab headscarves and modest clothing.
Widespread protests took place for a 12th straight night on Tuesday, according to opposition media based outside Iran, despite internet restrictions designed to impede gatherings and prevent images of the crackdown from getting out.
Women have burned their scarves and symbolically cut their hair in protest at Amini's death and the strict dress code, in solidarity rallies in many cities across the world.
'Blow to the head'
Fars news agency said on Tuesday that "around 60" people had been killed since Amini's death on September 16, up from the official toll of 41 authorities reported on Saturday.
But the Oslo-based group Iran Human Rights said the crackdown has killed at least 76 people.
Officials said Monday they had made more than 1,200 arrests, including activists, lawyers and journalists.
A cousin of Amini said she had been visiting Tehran with her family when she encountered the notorious morality police and died after a "violent blow to the head".
Amini was arrested along with her brother and female relatives after leaving an underground station despite being "dressed normally", Erfan Salih Mortezaee said.
"The police officer told (her brother), 'We are going to take her in, instil the rules in her and teach her how to wear the hijab and how to dress'," he told AFP news agency in Iraq.
"Amini's death has opened the doors of popular anger," said Mortezaee, who left Iran a year ago.
Shah's son hails 'women's revolution'
In an interview with AFP news agency, the son of Iran's late shah hailed the protests as a landmark revolution by women and urged the world to add to the pressure on the clerical leadership.
Reza Pahlavi, whose father was toppled in the Iranian Revolution of 1979, called for greater preparation for a future Iranian system that is secular and democratic.
"It is truly in modern times, in my opinion, the first revolution for the women, by the women — with the support of the Iranian men, sons, brothers and fathers," said Pahlavi, who lives in exile in the Washington area.
On Tuesday, authorities in Iran arrested the daughter of ex-president Akbar Hashemi Rafsanjani for "inciting rioters", the Tasnim news agency reported.
The crackdown has drawn condemnation from around the world.