The demonstrations have turned into a popular revolt by furious Iranians from all layers of society, posing one of the most significant legitimacy challenges to the Shi'ite clerical elite since the 1979 Islamic Revolution.

Nationwide protests, sparked by the death of 22-year-old Iranian Kurdish woman Mahsa Amini in September in the custody of morality police, have been at their most intense in the areas where the majority of Iran's 10 million Kurds live.

One video showed a member of Basij forces firing a gun at close range at students protesting at a branch of Azad University in Tehran. Gunshots were also heard in a video shared by rights group HENGAW from protests at the University of Kurdistan in Sanandaj.

Videos shared on social media showed protests in dozens of cities across Iran early on Sunday with hundreds of students participating despite the use of tear gas, clubs, rights groups said.

Rights groups say thousands have been arrested and hundreds injured in the crackdown waged by security forces.

Raisi will take over from pragmatist Hassan Rouhani on August 3 as Iran seeks to salvage the tattered nuclear deal and be rid of the US sanctions that have crippled Iran's economy.

Raisi was appointed by Khamenei as the judiciary chief in 2019.

Iran's clerical and military rulers have threatened revenge for Friday's killing of Mohsen Fakhrizadeh, which could further increase tensions in the Middle East region and beyond.

Iran's Atomic Energy Organisation initially reported that "an incident" had occurred at the facility in the central province of Isfahan.

Iran has the highest number of deaths from coronavirus outside China and close to 100 people are believed to be infected.

The Iran government threatens to take the third step if Europe fails to come through.

Britain has called Iran's capture of the Stena Impero in the Strait of Hormuz on Friday a "hostile act"

Iran has said that the Europeans have done “too little, too late” to salvage the pact by protecting Iran’s economic interests from US sanctions.

The latest sanctions are aimed at denying Iran’s leadership access to financial resources, blocking them from using the US financial system or having access to any assets in the US.

Zarif played the lead role in striking the deal under which Iran agreed to curbs on its nuclear programme in return for the lifting of international financial sanctions.

Soldiers, students, clerics and black-clad women holding small children thronged streets across Iran, many with portraits of Ayatollah Ruhollah Khomeini, the Shi'ite cleric who toppled the Shah in an Islamic uprising that still haunts the West.

Hours before the US was due to impose new sanctions on Iran post pulling out of the 2015 deal between both nations, Iranian President Rouhani rejected Trump's call for further talks.

Supreme Leader Ayatollah Ali Khamenei has ordered preparations to increase uranium enrichment capacity if a 2015 nuclear deal with world powers falls apart after the US withdrawal from it last month.

Protests erupted on December 28 in the holy Shi'ite city of Mashhad after the government announced plans to raise fuel prices and cut monthly cash handouts to lower-income Iranians.

At least 530 people were killed and thousands injured in the quake.