Protests erupted in Tehran and other Iranian cities Thursday evening, with demonstrators calling for the overthrow of Supreme Leader Ayatollah Ali Khamenei amid growing discontent over the country's economic situation. Videos verified by BBC Persian showed large crowds marching in Tehran and Mashhad, in what observers are calling the largest display of opposition to the clerical establishment in years.

The demonstrations, which remained peaceful and were not dispersed by security forces initially, followed 12 consecutive days of unrest triggered by the collapse of the Iranian currency. The protests have reportedly spread to over 100 cities and towns across all 31 of Iran's provinces, according to human rights groups.

Footage from the protests captured demonstrators chanting slogans in support of Reza Pahlavi, the exiled son of the late former Shah, who has urged his supporters to take to the streets.

The US-based Human Rights Activist News Agency (HRANA) reported that at least 34 protesters, including five children, and eight security personnel have been killed since the unrest began.

Following the demonstrations on Thursday, a monitoring group reported a nationwide internet blackout. The Iranian government has not yet commented on the reported internet shutdown or the extent of the protests.

The protests come at a time of heightened economic pressure on Iran, following the reimposition of sanctions by the United States after its withdrawal from the 2015 nuclear deal. The Iranian currency has plummeted in value, contributing to rising inflation and economic hardship for ordinary Iranians.

The situation remains fluid, and further developments are expected in the coming days. The government's response to the protests and the extent to which they continue to spread will be closely watched both domestically and internationally.