Iran has been shaken by its largest anti-government demonstrations in years overnight, with vast crowds filling streets in Tehran and a number of other major provincial cities, according to verified videos circulating online.

Footage from the capital and from Mashhad, Iran’s second city, shows sustained and largely peaceful marches on the evening of January 8 the BBC reports, a notable moment in a protest movement that security forces initially allowed to proceed without intervention. Shortly afterwards, monitoring groups reported a nationwide internet blackout – a fact that can be confirmed by bne IntelliNews, a now familiar tactic employed by the Iranian regime during periods of unrest.

The demonstrations mark the twelfth consecutive day of protests sparked by public anger over the collapse of the national currency and a deepening cost-of-living crisis. Human rights organisations say the unrest has now spread to more than 100 cities and towns across all 31 provinces, cutting across social and regional lines.

Videos from multiple locations depict crowds calling for the removal of the current supreme leader, the 86-year-old Ali Hosseini Khameni, and expressing support for the restoration of the former monarchy under Reza Pahlavi, the exiled son of Iran’s last shah who spends much of his time in the US and Germany bne sources say.

In Mashhad, protesters were seen dismantling what appeared to be Iran’s ubiquitous surveillance equipment from an overpass, underlining the movement’s increasingly confrontational edge.

Casualty figures vary at present with no reliable figures having yet been reported. According to the BBC, US-based and European monitoring groups report dozens of deaths among protesters, including children, alongside a number of fatalities among security personnel. Thousands of arrests have been recorded. Iranian authorities do, however, acknowledge a smaller number of deaths, largely among police and security forces.

The unrest has been particularly intense in western and north-western regions of the country with significant Kurdish and Lor populations. Rights groups say a call for a general strike by exiled Kurdish organisations led to widespread shop closures and clashes with security forces in several provinces. January 7 was described by monitors as the deadliest day so far, with lethal force used in multiple locations.

In the meantime, in recent days, state media has sought to minimise the scale of the protests, in some cases denying that demonstrations took place and broadcasting images of empty streets. At the same time, digital rights groups say internet connectivity across the country has been severely disrupted, hindering communication and reporting at a critical moment; a common modus operandi employed Iranian authorities at times of internal strife to prevent news of what is happening in the country from leaking out.

The protests were reignited in late December after a sharp fall in the rial, which has hit record lows amid soaring inflation, ongoing sanctions linked to Iran’s nuclear programme, and long-standing economic mismanagement by Tehran. At the time students quickly joined merchants and workers, turning economic grievances into broader political demands.

While President Masoud Pezeshkian has urged restraint by the country’s security forces, Khameni has supposedly drawn a distinction between protesters and what he described as rioters. As a result of the ongoing demonstrations and subsequent crackdown, international pressure is also mounting, with Washington warning of severe consequences should the crackdown intensify.