An independent fact-finding mission should investigate potential crimes against humanity committed by Iran, according to the UN-appointed representative looking into the regime's human rights abuses.
In an exclusive interview with ABC News, Mai Sato, special rapporteur on the situation of human rights in the Islamic Republic of Iran, estimated the number of civilians killed by the regime was at least 5,000.
The United Nations Human Rights Council would hold an emergency meeting and could re-establish an independent fact-finding mission into Iran that could investigate whether Supreme Leader Ali Khamenei should be referred to the International Criminal Court, she said.
She said she had heard reports from doctors inside Iran that the number of civilians killed could be 20,000 or more.
Last week, the United Nations Security Council held an emergency meeting to discuss the Islamic Republic's targeting of protesters.
After statements last week by US President Donald Trump that the United States may intervene, the council suggested the situation in Iran was best addressed through diplomacy and dialogue.
But human rights groups and NGOs are calling for an emergency session of the UN Human Rights Council — which does not rely on veto powers of China and Russia — to address mass killings of protesters.
Unlike the Security Council, the Human Rights Council can establish investigations and make recommendations to member states.
Ms Sato told ABC News there could be an emergency Human Rights Council session as early as this week that could call for the continuation of an international fact-finding mission that was created after the 2022 Women, Life, Freedom protests.
"They could be mandated to investigate this [latest] protest and the human rights impact in order to collect evidence and hold people accountable," she said.
Ms Sato said the international fact-finding mission's mandate was set to come to an end in March and could be extended.
Investigating crimes against humanity
Asked whether she believed crimes against humanity had been committed, Ms Sato said there may have been, but investigation was required.
"Crimes against humanity [are] defined as widespread, systematic human rights violations against civilians, and that includes murder, torture, arbitrary detention," she said.
"There also needs to be intent. There [have] been so many casualties, and I have seen so many videos of security forces opening fire to unarmed civilians.
"But I think what we are seeing is extremely serious and after that I think the fact-finding mission, which is already in place, will be best placed to investigate that."
Similarly, when asked about the potential for Mr Khamenei and other people within the regime to be referred to the International Criminal Court, Ms Sato said an investigation would need to come first.
Ms Sato said any potential prosecution of Iran's rulers for crimes against humanity could either "take place at the ICC or states could exercise universal jurisdiction".
The latter refers to the ability of a national court to prosecute individuals for serious crimes against international law.
The ABC has verified videos showing protesters shot in the face and hundreds of bodies lined up outside morgues in massacres committed by regime forces.
An internet blackout has made it extremely difficult to reach Iranians inside the country, but some protesters who broke through to speak with the ABC via a Starlink connection have been calling for the United States and the wider international community to step in and support them.
Ms Sato, who had been investigating the regime's human rights abuses before the latest protests broke out, noted record numbers of executions in Iran took place last year.
The Norwegian-based Iran Human Rights (IHR) group said it had verified at least 1,500 executions up until the start of December, adding many more had taken place since.
Ms Sato was worried, under the communications blackout and despite public assurances from the regime, the Islamic Republic could continue with executions and numbers could again rise.
"The death penalty in Iran has been a serious concern," Ms Sato said.
"We need to think about the death penalty not just in terms of the number of executions, but as a form of coercive threat … that is a way to exert control over its citizens. And we may see a rise in executions."
'5,000 to 20,000' killed by regime
Ms Sato said the Islamic Republic was deliberately attempting to conceal the mass killing of protesters on the street by shutting down the internet, as well as the telecommunications network.
She had seen horrific videos of people injured and had received reports that when families received the bodies of loved ones, they were forced to sign a paper identifying them as part of Basij paramilitary forces, rather than a civilian.
In some cases, families were forced to pay up to $US7,000 ($10,400) to collect their loved ones' bodies, she said.
Videos shared with the ABC appear to show distraught families searching for loved ones, trying to identify them, and in some cases, wailing beside their lifeless bodies.
The near-total internet blackout that has covered Iran has made it impossible to independently verify the number of people killed.
The US-based Human Rights Activists News Agency's (HRANA's) latest figure on the number of confirmed fatalities has reached 4,029, while the number of fatalities under review stands at 9,049.
Additionally, the group said at least 5,811 people sustained severe injuries during the protests, and the total number of arrests had risen to 26,015.
When asked about a separate report compiled by doctors inside Iran and shared with ABC News that at least 16,500 protesters had been killed and about 330,000 injured, Ms Sato said she was receiving similar figures.
"I would put the minimum estimates … to be 5,000-plus and that's sort of the more conservative organisations reporting that figure," she said.
"But … also Iranian authorities have said it will be around 5,000 deaths, so I think that is the minimum.
"And then I've also received reports up to 20,000 — they have been largely through courageous doctors with access to Starlink being able to provide information of people who they've received in hospital."
Ms Sato said not all doctors were able to provide information.
"I think the actual number, once we have more information, will be significantly higher," she said.
There are concerns from human rights organisations that Iran's internet blockade could be protracted, leading to extreme digital isolation of the country's citizens.
Ms Sato said to address this, the Geneva-based International Telecommunication Union, an agency of the United Nations that aims to facilitate international cooperation and improve telecommunication infrastructure in the developing world, could be asked to step in and help.
She said the ITU could be urged by UN member states "to make a strong statement about the internet shutdown" and that could then lead to countries stepping in to assist with connections when needed.
Will UN member countries take 'bold action' against Iran's rulers?
While Ms Sato had seen videos of Iranian protesters calling for US intervention, she hoped there would instead be multilateral action.
Behnam Ben Taleblu, senior director of the Washington-based Foundation for Defense of Democracies Iran Program, which is staunchly anti-regime, said UN member states needed to take "bold national efforts" to help the Iranian people.
"It's high time to beef up the existing UN fact-finding mission on Iran and either extend or amend its mandate or push for a new one altogether given what is fast appearing to be the most violent crackdown … from the state against the street in contemporary Iranian history," he told ABC News.
"?While nowhere near sufficient, international naming and shaming is necessary. It was clearly critical enough that even US President Donald Trump told Iranians to keep lists of their oppressors."
Mr Taleblu said the international community should now move quickly to determine if and how the ICC might be able to prosecute Iranian officials, including Mr Khamenei and Supreme National Security Council Secretary Ali Larijani, who is widely considered one of the architects of the crackdown and was sanctioned by the US Department of Treasury last week.
"While this is complicated by Iran not being a party to the Rome statute [the government framework for the ICC], United Nations Security Council referral to the court by member states or dossiers submitted to the ICC prosecutor by activists and lawyers in member states could help to pave the way," he said.
Mr Taleblu also called on individual member states not to "take solace in an exclusively international and legal process".
He said member states were required to follow up on important diplomatic efforts of entities like the World Economic Forum and the Munich Security Conference, which have now refused to invite Iran's Foreign Minister Abbas Araghchi to their high-profile conferences.
"The message should be clear: it's high time to roll up the diplomatic red carpet for the Islamic Republic and stand with the Iranian people," he said.
Ms Sato would not predict whether the regime would ultimately fall, but noted that protests started in Tehran with the merchants expressing dissatisfaction and strong dissent over the state of Iran's economy.
She said her previous UN reports had noted the economic crisis and questioned how it would be possible, under such circumstances, for the regime to carry on.
"It's difficult for me to say. But [Iran's] people have spoken up, not just about the dissatisfaction about economy, but about the governance," she said.
"And they're potentially asking for governmental change. And they have the right to exercise that."
Ms Sato's reports have also looked at how the regime has been engaging in "transnational repression", which includes targeting of Iranian journalists and activists abroad.
"I think it happens at two levels outside and also inside the country. I haven't received reports of that having escalated during the protest, but I think that is to do with the shutdown that's happening at the moment," she said.
"I've been informed of cases in Australia and also in other countries as well. And I think governments are starting to take serious notice of how serious transnational repression is."
