Iran is responsible for the “physical violence” that led to the death of Mahsa Amini in September 2022 and sparked nationwide protests against the country's mandatory headscarf, or hijab, laws and its ruling theocracy, a UN fact-finding mission said on Friday.

The stark pronouncement came in a wide-ranging initial report submitted to the UN Human Rights Council by the Fact-Finding Mission on Iran.

It also found that the Islamic Republic employed “unnecessary and disproportionate use of lethal force” to put down the demonstrations that erupted following Amini's death, and that Iranian security forces sexually assaulted detainees.

The monthslong security crackdown killed more than 500 people and saw over 22,000 detained.

There was no immediate comment on the report from Iran. Iranian officials did not respond to requests for comment from The Associated Press on the mission's findings.

The release of the report is unlikely to change the trajectory of Iran's government, now more firmly in the hands of hard-liners after a low-turnout vote last week put them back in charge of the country's parliament.

However, it provides further international pressure on Tehran amid wider Western concerns about its advancing nuclear program, Iran's arming of Russia in Moscow's war on Ukraine and the continued harassment and imprisonment of activists, including Nobel Peace Prize laureate Narges Mohammadi.

“The protests were unprecedented because of the leadership of women and youth, in their reach and longevity and, ultimately, the state's violent response,” the report says.

Amini, 22, died on September 16, 2022, in a hospital after her arrest by the country's morality police over allegedly not wearing her hijab to the liking of the authorities. She was brought to Iran's Vozara detention facility to undergo a “re-education class", but collapsed after 26 minutes and was taken to a hospital 30 minutes later, according to the report.

Iran has denied being responsible for her death or that she had been beaten. At times, authorities have pointed to a medical condition Amini had from childhood after a surgery. The UN report dismissed that as a cause of her death.

The panel "has established the existence of evidence of trauma to Ms. Amini's body, inflicted while in the custody of the morality police", the report says.

“Based on the evidence and patterns of violence by the morality police in the enforcement of the mandatory hijab on women, the mission is satisfied that Ms. Amini was subjected to physical violence that led to her death,” it said.

The report stops short, however, of blaming anyone specifically for harming Amini.

The protests that followed Amini's death started first with the chant “Women, Life, Freedom.” However, the protesters' chanting and cries soon grew into open calls of revolt against Iranian Supreme Leader Ayatollah Ali Khamenei.

The UN report found Iranian security forces used shotguns, assault rifles and submachine guns against demonstrators “in situations where there was no imminent threat of death or serious injury" to them, “thereby committing unlawful and extrajudicial killings”.

It also found a pattern of protesters being shot intentionally in the eye.

“The mission notes the deterrent and chilling effect of such injuries, as they permanently marked the victims, essentially branding' them as protesters,” the report says.

Some of those detained faced sexual violence, including rape, the threat of rape, forced nudity, groping and electrocution of their genitals, according to the report.

“The security forces played on social and cultural stigma connected to sexual and gender-based violence to spread fear and humiliate and punish women, men and children,” the report says.

The panel also acknowledged it continued to investigate the 2023 death of teenager Armita Garavand, who died after falling on the Tehran Metro in what activists allege was an attack over her not wearing a hijab.

Geravand's parents appeared in a state media video at the time saying a blood pressure issue, a fall or perhaps both contributed to their daughter's death.

“In actions reminiscent of Ms. Amini's case, the state authorities took measures to obfuscate the circumstances leading to Ms. Garavand's death,” the report says.

It also noted a suspected spate of poisonings targeting Iranian schoolgirls, without drawing conclusions on what transpired in the incidents.