The death toll from Iran's ongoing protests could surge, and a government crackdown could reach new levels of violence as the nation's internet shutdown stretches on for a fifth day.
Human rights groups estimate more than 500 people have been killed and more than 10,600 arrested in the ongoing protests.
Few videos have been published on social media, and verifying information has become difficult.
Those watching from outside the nation's borders warn the number of deaths and the number of detainees could soar once the blackout is lifted.
Arina Moradi is a member of the Hengaw Organisation for Human Rights, an independent Kurdish group monitoring human rights violations in Iran.
"We have seen in the past that whenever they shut down [the] internet, it's because they want to use, as much as possible, their violence and their method of controlling people using violence," she said.
Widespread protests sparked an internet shutdown
Protests began in late December.
As the Iranian rial crashed to a record low against the US dollar, merchants in the capital, Tehran, shut their doors.
From there, demonstrations against the regime have spread across multiple demographics and across multiple cities.
Some who spoke to the ABC from inside Tehran said people had been pushed to "desperation".
Iran's security forces have quickly escalated their repression, in some cases moving from tear gas to live ammunition in an effort to halt protesters.
The scale of the protests, Ms Moradi told the ABC, had changed rapidly — with demonstrations in hundreds of cities and towns across at least 31 provinces so far.
"It started in Tehran, and it was over economic hardship and the poor living situation," she told the ABC.
"But the demands we can see now [are] much bigger and deeper than this.
"It's very diverse, and people are calling for their basic rights to be protected, for freedom, and even for … an end to the Islamic Republic of Iran."
Protests reached a high point on January 8, spreading across multiple major cities.
According to the Oslo-based non-governmental organisation Iran Human Rights, at least 50 Kurdish cities took part in a general strike.
By 10pm, local time, that day, the internet was shut down across Iran.
NetBlocks, an independent group mapping internet freedom around the world, stated that at least 99 per cent of Iran's internet was under a blackout by the following morning.
The group's London-based founder Alp Toker told the ABC the outage ranked among the top 10 longest internet blackouts they had ever recorded globally.
"This kind of total shutdown is very costly to the regime itself, to the economy. It's an extreme measure," he said.
Iran's 'kill switch' blackout raises concerns about unseen violence
Iran uses a kind of "internet kill switch", meaning it has full control over the network's infrastructure.
National connectivity remained at just 1 per cent of ordinary levels, according to NetBlocks, on day four of the shutdown.
Overnight, internet traffic in Iran dropped to "effectively zero", according to online monitor Cloudflare Radar.
Iranian authorities imposed nationwide internet blackouts in response to protests in 2019 and 2022 — as well as during a 12-day war with Israel in 2025.
"It is a go-to tactic," Mr Toker said.
"The technology is advancing. A process that was quite manual in 2019 with the step-by-step disconnection of networks … has now been automated."
"By 2025, it had already become essentially a kill switch — it's a one-step process to switch the country offline.
"What we've seen here is basically a repeat of what happened during the Israel–Iran war. We've seen also the restriction of phone calls and fixed-line phones to the outside world as well."
That previous crackdown in 2022 led some to turn to the Starlink satellite system, owned by Elon Musk's SpaceX, for access.
Independent financial news outlet TechStock2 estimated 10,000 to 20,000 Starlink terminals were operating inside Iran as of late 2024.
The small, rectangular devices allowed Iranians to access uncensored internet during past shutdowns.
This time around, however, the government appeared to target Starlink also — a move some experts, including internet researcher Amir Rashidi, had never seen before.
Military-grade jamming signals were targeting Starlink satellites, Mr Rashidi told online outlet TechRadar.
"I have been monitoring and researching access to the internet for the past 20 years, and I have never seen such a thing in my life," he said.
Majid Sadeghour is an Iranian-American human rights activist and political director of Washington-based non-profit, the Organization of Iranian American Communities.
He told the ABC the regime would continue the blackout "until it either folds or massacres people to end the uprising".
"The fundamental reason is that this time, the protests are much more organised," he said.
"[They] include nearly all age groups and social segments, and are led by core groups of resistance units.
"In internet and communication darkness, the regime is engaged in a virtual nationwide massacre.
"This time, the regime is facing an existential internal crisis."
Donald Trump warns of 'strong options' as protests continue
With the blackout, the scale of the protests has become difficult to discern.
People near borders could get some mobile reception from a neighbouring country, Mr Toker said, which was how updates were continuing to trickle out of Iran.
"But they don't necessarily know what is happening in the rest of the country," he said.
"It doesn't get information from Tehran."
The United States has warned Iranian leaders against using force.
Late on Sunday, local time, US President Donald Trump told reporters on Air Force One that Washington was considering "strong options", including military intervention.
"The military is looking at it, and we're looking at some very strong options," he said.
Iranian leaders have said any attack on Iran would make both Israel and all US bases and ships a "legitimate target".
Emma Briant, an expert in information warfare and propaganda at the University of Notre Dame's Lucy Institute for Data and Society, said Mr Trump's potential intervention could backfire.
"I think it's evident that Trump's recent intervention in Venezuela was seen as an easy win, and the administration has been emboldened in its international ambitions," Dr Briant said.
"[But] the Iranian regime casts domestic protests as the product of Anglo-American interference — linked to the quest for oil, or meddling from Israel.
"If foreign bombing were to destroy the infrastructure of the government, the power vacuum and loss of infrastructure would be incredibly destabilising and would make it impossible for the country to rebuild.
"With the advances in internet disruption, the regime has made it much harder to organise, aiming to fragment the uprising. It is harder to know how strong your movement is, [and] fear and propaganda spread.
"If the protests are to be successful, they need to find ways to communicate and organise."
