Helen Sullivan,BBC News,
Shayan Sardarizadeh & Richard Irvine-Brown,BBC Verifyand
Sarah Namjoo,BBC Persian
Watch: Protesters and security forces clash in Iran protests
Protesters in Iran defied a government crackdown on Saturday night, taking to the streets despite medics at two hospitals telling the BBC more than 100 bodies have been brought in over a two day period.
Videos verified by the BBC and eyewitness accounts appeared to show the government was ramping up its response.
Iran's attorney general said anyone protesting would be considered an "enemy of God" - an offence that carries the death penalty.
US President Donald Trump has threatened to hit Iran "very hard" if they "start killing people". Iran's parliament speaker warned that if the US attacks Iran, Israel and all US military and shipping bases in the region would be legitimate targets.
The protests were sparked by soaring inflation, and have spread to more than 100 cities and towns across every province in Iran. Now protesters are calling for an end to the clerical rule of Iran's Supreme Leader Ayatollah Ali Khamenei.
Khamenei has dismissed demonstrators as a "bunch of vandals" seeking to "please" Trump.
Trump on Saturday said the US "stands ready to help" as Iran "is looking at FREEDOM".
As protests intensify, the number of deaths and injuries continues to rise. Two human rights groups have reported more than 100 people, including security personnel, killed.
Staff at several hospitals told the BBC they have been overwhelmed with the injured and dead, with BBC Persian verifying 70 bodies brought to one hospital in Rasht city on Friday night and a health worker reporting around 38 people dying at a Tehran hospital.
Iran's police chief said on state TV that the level of confrontation with protesters had been stepped up, with arrests on Saturday night of what he called "key figures". He blamed a "significant proportion of fatalities" on "trained and directed individuals", not security forces, but did not give specific details.
More than 2,500 people have been arrested since protests began on 28 December, according to a human rights group.
The BBC and most other international news organisations are unable to report from inside Iran, and the Iranian government has imposed an internet shutdown since Thursday, making obtaining and verifying information difficult.
MAHSA / Middle East Images / AFP via Getty ImagesProtesters gathered in a street in Tehran on Friday, 9 January
Nonetheless, some video footage has emerged, and the BBC has spoken to people on the ground.
Several videos, confirmed as recent by BBC Verify, show clashes between protesters and security forces in Mashhad, Iran's second largest city.
Masked protesters are seen taking cover behind bins and bonfires, while a row of security forces is seen in the distance. A vehicle that appears to be a bus is engulfed in flames.
Multiple gunshots and what sounds like banging on pots and pans can be heard.
A figure standing on a nearby footbridge appears to fire multiple gunshots in several directions as a couple of people take cover behind a fence.
In Tehran, a verified video from Saturday night shows protesters also taking over the streets in the Gisha district.
Other verified videos from the capital show a large group of protesters and the sound of banging on pots in Punak Square, and a crowd of protesters marching on a road and calling for the end of the clerical establishment in the Heravi district.
Internet access in Iran is largely limited to a domestic intranet, with restricted links to the outside world. But during the current round of protests, authorities have for the first time severely restricted the domestic intranet.
An expert told BBC Persian the shutdown is more severe than during the "Women, Life, Freedom" uprising in 2022.
Alireza Manafi, an internet researcher, said the only likely way to connect to the outside world was via Starlink satellite internet, but warned users to exercise caution, as such connections could potentially be traced by the government.
US 'ready to help'
On Saturday, Trump wrote on social media: "Iran is looking at FREEDOM, perhaps like never before. The USA stands ready to help!!!"
He did not elaborate, but US media reported that Trump had been briefed on options for military strikes in the country. The New York Times and Wall Street Journal (WSJ) reported the briefings had taken place, with WSJ describing them as "preliminary discussions". An unnamed official told the WSJ there was no "imminent threat" to Iran.
Last year, the US conducted airstrikes on Iranian nuclear facilities.
On Sunday, Reza Pahlavi, the exiled son of Iran's last shah (king), who lives in the US and whose return protesters have been calling for, posted a video to X.
Its caption said: "Your compatriots around the world are proudly shouting your voice... In particular, President Trump, as the leader of the free world, has carefully observed your indescribable bravery and has announced that he is ready to help you."
He added: "I know that I will soon be by your side."
He claimed the Islamic Republic was facing a "severe shortage of mercenaries" and that "many armed and security forces have left their workplaces or disobeyed orders to suppress the people". The BBC could not verify these claims.
Pahlavi encouraged people to continue protesting on Sunday evening, but to stay in groups or with crowds and not "endanger your lives".
Watch: Protesters take to the streets of Tehran on Friday night
Amnesty International said it was analysing "distressing reports that security forces had intensified their unlawful use of lethal force against protesters" since Thursday.
UK Foreign Secretary Yvette Cooper said those speaking out against Khamenei's government should not face "the threat of violence or reprisals".
At least 78 protesters and 38 security personnel have been killed in the past two weeks, US-based Human Rights Activists in Iran said.
Norway-based Iran Human Rights reported at least 192 protesters have been killed.
The group's director Mahmood Amiry-Moghaddam said: "The killing of protesters over the past three days, particularly following the nationwide internet shutdown, may be even more extensive than we currently imagine."
BBC Persian has confirmed the identities of 26 people killed, including six children.
The protests have been the most widespread since an uprising in 2022 sparked by the death in custody of Mahsa Amini, a young Kurdish woman who was detained by morality police for allegedly not wearing her hijab properly.
More than 550 people were killed and 20,000 detained by security forces over several months, according to human rights groups.
Additional reporting by Soroush Pakzad and Roja Assadi