Iranian authorities are restricting communications access as protests against the country's theocratic regime escalate.
The internet monitoring group NetBlocks reported a nationwide blackout late on Thursday night, local time, which it said followed "a series of escalating digital censorship measures".
The internet blackout was hindering "the public's right to communicate at a critical moment", the London-based company said.
People in Iran's capital shouted from their homes and rallied in the street on Thursday night, witnesses said — a new escalation in the protests that have spread across the Islamic Republic.
Renewed demonstrations came after Reza Pahlavi — the exiled son of Iran's late Shah, toppled in the 1979 Islamic Revolution — called for more protests in a video post on X on Wednesday.
Iraq-based Iranian Kurdish opposition parties called for a general strike on Thursday in Kurdish-populated areas in western Iran.
Posts on social media, which could not be independently verified, said demonstrators chanted pro-Pahlavi slogans in several cities and towns across Iran.
Videos posted earlier to social media showed large crowds of protesters marching through the capital, Tehran, and other major cities.
Witnesses said crowds in Mashhad — a holy city known as a conservative, religious stronghold sympathetic to the regime — called for the overthrow of Ayatollah Ali Khamenei.
Iranian state media claimed cities around the country were calm.
Trump warns Iran will 'pay hell' if protesters killed
US President Donald Trump on Thursday reiterated a warning to Iranian officials: "If they start killing people, which they tend to do during their riots … we're going to hit them very hard."
According to the Norway-based Iran Human Rights organisation, at least 45 people have been killed in Iran since last month, including eight children.
"The evidence shows that the scope of the crackdown is becoming more violent and more extensive every day," said its director, Mahmood Amiry-Moghaddam.
Iran Human Rights said on Wednesday was the deadliest day so far, with 13 protesters confirmed to have been killed.
Asked by US broadcaster Hugh Hewitt about dozens of deaths that had already occurred, Mr Trump suggested there had been "stampedes" which Iranian officials could not be held responsible for.
But if they shot protesters, he said, "they're going to have to pay hell".
The latest protests began last month in Tehran's Grand Bazaar with shopkeepers condemning the rial currency's free fall.
They are the country's largest since the protest wave in 2022 and 2023 sparked by the death in custody of Mahsa Amini, who had been arrested for allegedly violating the strict dress code for women.
High inflation has been driven by economic mismanagement and Western sanctions, compounding public anger over political and social restrictions imposed by the theocratic regime.
On Thursday, Iranian President Masoud Pezeshkian called for "utmost restraint" in handling demonstrations, saying that "any violent or coercive behaviour should be avoided".
Deakin University research fellow Ali Mamouri said the Iranian regime was exhibiting relative tolerance regarding current protests compared to its violent crackdowns in 2022, during which rights groups estimate hundreds were killed.
"They are very well aware of the consequences that might happen if they take the wrong action against the protesters," he said.
Rights groups slam 'unlawful force' by Iranian officials
US-based Human Rights Activists News Agency reported violence at demonstrations had left at least 41 people dead while more than 2,270 others had been detained since late December.
It said rallies had taken place in 348 locations in all of Iran's 31 provinces.
Rights groups have also accused authorities of resorting to tactics, including raiding hospitals to detain wounded protesters.
Amnesty International accused Iranian security forces of using "unlawful force" against both protesters and bystanders.
Speaking on Thursday, Mr Trump said Iranians were "brave people".
"It's a shame what's happened to your country. Your country was a great country," he said.
He last week warned on social media that if Iranian authorities shot protesters, "the United States of America will come to their rescue".
"We are locked and loaded and ready to go," he said.
Germany's Foreign Minister Johann Wadephul condemned Iranian officials' "excessive use of force" against protesters.
Mr Pahlavi, who lives in the US, thanked Mr Trump and called upon European leaders to "act more decisively" in support of the people of Iran.
"I call on them to use all technical, financial and diplomatic resources available to restore communication to the Iranian people so that their voice and their will can be heard and seen," he said.
"Do not let the voices of my courageous compatriots be silenced."
Dr Mamouri said that, while supporters of Mr Pahlavi were mobilising, the collapse of the Islamic Republic remained unlikely.
"Despite all the pressure and all the problems, there is still functionality in the system," he said.
"The regime is still strong enough to continue for some more years."
Calls for release of Nobel laureate
Nobel Peace Prize laureate Narges Mohammadi remains imprisoned by authorities after her arrest in December.
"The people of Iran have taken to the streets, just as they did in 2009, 2019," her son Ali Rahmani said.
"Each time, the same demands came up: an end to the Islamic Republic, an end to this patriarchal, dictatorial and religious regime, the end of the clerics, the end of the mullahs' regime."
The Norwegian Nobel Committee has called on Iranian authorities to "immediately clarify Mohammadi's whereabouts, ensure her safety and integrity, and to release her without conditions".
ABC/Wires
