The United Nations Human Rights Council has voted to appoint an independent investigation into Iran's deadly repression of protests, passing the motion to cheers of activists amid an intensifying crackdown in Kurdish areas over recent days.
Volker Turk, the UN rights commissioner, had earlier demanded that Iran end its "disproportionate" use of force in quashing protests that have erupted after the death in custody of 22-year old Kurdish woman Mahsa Amini on September 16.
The protests have particularly focused on women's rights - Amini was detained by morality police for attire deemed inappropriate under Iran's Islamic dress code - but have also called for the fall of Supreme Leader Ayatollah Ali Khamenei.
The unrest has posed one of the boldest challenges to Iran's clerical ruling elite since it came to power in the 1979 Islamic revolution although authorities have crushed previous rounds of major protests.
US Secretary of State Antony Blinken welcomed the vote.
"Today's session leaves no doubt that the HRC's membership recognises the gravity of the situation in Iran, and the fact-finding mission established today will help ensure that those engaged in the ongoing violent suppression of Iranian people are identified and their actions documented," he said in a statement.
The mission will collect evidence into abuses during the authorities' deadly crackdown.
Evidence assembled by a mission appointed by the same council was later used for the prosecution of a Syrian ex-officer in Germany who was accused of war crimes.
Iran's representative at the Geneva meeting Khadijeh Karimi earlier accused the United States and its allies of using the council to target Iran, a move she called "appalling and disgraceful".
Turk, who said Iran faced a "full fledged human rights crisis" with 14,000 people arrested, including children, said Iran's government had not responded to his request to visit the country.
Iran has given no death toll for protesters but a deputy foreign minister, Ali Bagheri Kani, said on Thursday that about 50 police had died and hundreds been injured in the unrest - the first official figure for deaths among security forces.
He did not say whether that figure also included deaths among other security forces such as the Revolutionary Guards.
The crackdown has been particularly intense in Kurdish areas, located in western Iran, with the UN rights monitor this week noting reports of 40 deaths there over the past week.
Voria Ghafouri, an outspoken Kurdish Iranian football player, was arrested on Thursday for "insulting the national team" and "propaganda against the system," according to the official IRNA news agency.
He was arrested after a training session with the Foolad Khuzestan Football Club.
Iranian authorities have arrested a number of football players for expressing their support for protests.
Asked on Thursday about the unrest at home Iran team striker Mehdi Taremi said they were in Qatar to play football.
"We are not under pressure," he added after players refused to sing the national anthem in their first match at the World Cup against England.
Prominent Sunni Muslim cleric Molavi Abdulhamid, a member of the Baluch minority in the southeast who has been outspoken in criticising the treatment of mostly Sunni ethnic minorities by the mainly Shi'ite ruling elite, spoke against the crackdown.
"The dear Kurds of Iran have endured many sufferings such as severe ethnic discrimination, severe religious pressure, poverty and economic hardships. Is it just to respond to their protest with war bullets?" he tweeted on Wednesday.