Protests have taken place across the country, with BBC Verify verifying videos from 67 locations.
On Friday, protesters amassed after weekly prayers in the south-eastern city of Zahedan, videos verified by BBC Persian and BBC Verify show. In one of the videos, people can be heard chanting “death to the dictator”, referencing Khamenei.
In another, protesters gather near a local mosque, when several loud bangs can be heard.
Another verified video from Thursday showed a fire at the office of the Young Journalists Club, a subsidiary of state broadcaster Irib, in the city of Isfahan. It is unclear what caused the fire and if anyone was injured.
Photos received by the BBC from Thursday night also show cars overturned and set alight at Tehran’s Kaaj roundabout.
The country has been under a near-total internet blackout since Thursday evening, with minor amounts of traffic returning on Friday, internet monitoring groups Cloudfare and Netblocks said. That means less information is emerging from Iran.
IHRNGO director Mahmood Amiry-Moghaddam said in a statement that “the extent of the government’s use of force against protesters has been increasing, and the risk of intensified violence and the widespread killing of protesters after the internet shutdown is very serious”.
Nobel laureate Shirin Ebadi has warned of a possible “massacre” during the internet shutdown.
One person who was able to send a message to the BBC said he was in Shiraz, in southern Iran. He reported a run on supermarkets by residents trying to stock up on food and other essentials, expecting worse days to come.