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" US President Donald Trump.
Trump has threatened to hit Iran "very hard" if they "start killing people".
Iranian Parliament Speaker Mohammad Baqer Qalibaf on Sunday warned that if the US attacks Iran, Israel and all US military and shipping bases in the region will be legitimate targets for Iran to attack.
As protests intensify, the number of deaths and injuries continues to rise. BBC sources and US-based Human Rights Activists in Iran (HRANA) have reported more than 100 people, including security personnel, killed.
Staff at three 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.
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.
Nonetheless, some video footage has emerged, and the BBC has spoken to people on the ground.
Verified video from Saturday night showed protesters taking over the streets in Tehran's Gisha district. 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 wheelie 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 is visible in the footage and appears to fire multiple gunshots in several directions as a couple of people take cover behind a fence on the side of Vakil Abad Boulevard.
Another verified video shows a large group of protesters and the sound of banging on pots in Punak Square in west Tehran.
A clip filmed in the Heravi district in north-east Tehran, confirmed by BBC Persian and BBC Verify, shows a crowd of protesters marching on a road and calling for the end of the clerical establishment.
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, not only shut down access to the worldwide internet but also severely restricted the domestic intranet.
An expert told BBC Persian the shutdown is more severe than that imposed during the "Women, Life, Freedom" uprising in 2022. Alireza Manafi, an internet researcher, said internet access in Iran, in any form, was now "almost completely down".
He added 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.