Thousands of Iranians took to the streets in support of the government for a fourth-straight day chanting "death" to foreign nations accused of instigating deadly unrest that began last month.

State television showed pro-government rallies in cities including Amol, Semnan, and Shadegan with supporters waving Iranian flags and chanting "Death to America", "Death to Israel", and "Death to Britain".

State TV described the rallies as a "response to rioters and supporters of the riots".

Iran's chief prosecutor Mohammad Jafar Montazeri on Thursday accused the American CIA, Israel's Mossad spy agency, and Saudi Arabia of orchestrating the anti-government demonstrations that led to the deaths of 22 people, along with hundreds of arrests.

Saturday's rallies came after the United Nations Security Council (UNSC) - at the request of the United States - held an emergency meeting on Friday to discuss Iran's protests.

Tehran's foreign minister called out the US government for raising a domestic issue before the international body.

"The UNSC rebuffed the US's naked attempt to hijack its mandate... Another FP [foreign policy] blunder for the Trump administration," Foreign Minister Mohammad Javad Zarif said on Twitter.

The UNSC rebuffed the US' naked attempt to hijack its mandate. Majority emphasized the need to fully implement the JCPOA and to refrain from interfering in internal affairs of others. Another FP blunder for the Trump administration. Iran's statement: https://t.co/QsbihBW69V — Javad Zarif (@JZarif) January 5, 2018

Unrest spread to more than 80 cities and rural towns late last month as thousands of young and working class Iranians voiced anger at corruption, unemployment, and a deepening gap between rich and poor in the biggest anti-government demonstrations since 2009.

Those protests have petered out in recent days while pro-government rallies have gained momentum.

About 1,000 people are estimated to have been arrested during the demonstrations. Videos appearing on social media in recent days showed relatives of detainees gathering outside prisons to seek information about the fate of their loved ones.

Tehran University Vice President Majid Sarsangi said the university had set up a committee to track the fate of students arrested during the unrest.

"Our efforts at the university are aimed at cooperating with the relevant authorities to create the conditions for the return of the detained students to the university and their families in the shortest possible time," Sarsangi told ISNA news agency.

The provincial governor in northeastern Mashhad, where the protests started, was quoted as saying on Saturday that 85 percent of detainees there had been released after signing a pledge not to re-offend.

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"Those with a criminal record, or those charged with sabotage such a setting fire to motorcycles or damaging public buildings have been referred to judicial authorities," governor Alireza Rashidian was quoted by ISNA as saying.

On Saturday, Iranians were able to access the photo-sharing site Instagram again after it was blocked for the past week.

The government suspended access to the messaging app Telegram, which was being used to publicise the protests. Twitter and Facebook were already banned.