Huge crowds of protesters have been marching through Iran's capital and other cities, videos show, in what is said to be the largest show of force by opponents of the clerical establishment in years.
The peaceful demonstrations in Tehran and the second city of Mashhad on Thursday evening, which were not dispersed by security forces, can be seen in footage verified by BBC Persian.
Later, a monitoring group reported a nationwide internet blackout.
Protesters can be heard in the footage calling for the overthrow of Iran's Supreme Leader Ayatollah Ali Khamenei and the return of Reza Pahlavi, the exiled son of the late former shah, who had urged his supporters to take to the streets.
It was the 12th consecutive day of unrest that has been sparked by anger over the collapse of the Iranian currency and has spread to more than 100 cities and towns across all 31 of Iran's provinces, according to human rights groups.
The US-based Human Rights Activist News Agency (HRANA) has said at least 34 protesters - five of them children - and eight security personnel have been killed, and that 2,270 other protesters have been arrested.
Norway-based monitor Iran Human Rights (IHR) has said at least 45 protesters, including eight children, have been killed by security forces.
BBC Persian has confirmed the deaths and identities of 22 people, while Iranian authorities have reported the deaths of six security personnel.
Iranian state media downplayed the scale of Thursday's unrest. In some cases, they denied protests had taken place altogether, posting videos of empty streets.
Meanwhile, internet watchdog NetBlocks said its metrics showed that Iran was "in the midst of a nationwide internet blackout".
www.bbc.co.uk/news/articles/cg7y0579lp8o