Iran's clerical rulers faced mounting international pressure over their crackdown on protests, with France's president characterising the unrest as a revolution and European governments planning sanctions on the Revolutionary Guards.

The nationwide protests, ignited by 22-year-old Mahsa Amini's death in morality police custody on 16 September after her arrest for "inappropriate attire", have turned into a legitimacy crisis for the four-decade-old Islamic Republic.

"Something unprecedented is happening," France's Emmanuel Macron told France Inter radio. "The grandchildren of the revolution are carrying out a revolution and are devouring it."

Mr Macron said the crackdown by Iranian leaders would make it harder to reach agreement on reviving the 2015 nuclear deal, which would give Iran sanctions relief in exchange for curbs on its nuclear programme.

"This revolution changes many things," Mr Macron said. "I don't think there will be new proposals which can be made right now to save the nuclear deal."

Meanwhile, Britain said it was sanctioning two dozen Iranian officials including a government minister over what it called a "violent repression of protests" sparked by Ms Amini's death.

The sanctions, coordinated with international partners, include Iranian Communications Minister Issa Zarepour as well as the chief of its cyber police, Vahid Mohammad Naser Majid, and a range of political and security officials, the British foreign office said in a statement.

"These sanctions target officials within the Iranian regime who are responsible for heinous human rights violations," Foreign Secretary James Cleverly said.

The sanctions include asset freezes and travel bans.

Women and students have played a leading role calling for the downfall of Islamist rule under Supreme Leader Ayatollah Ali Khamenei, in defiance of a tough crackdown by security forces.

German Foreign Minister Annalena Baerbock said this morning that new European sanctions would include targeted measures at "the inner circle" of the Revolutionary Guard - the main paramilitary force in charge of protecting the Shia clerical ruling system - and financing structures.

"We will pass a new sanctions package to send a clear signal to those responsible who think they can oppress, intimidate and kill their own people without consequences," she said before a meeting with other EU foreign ministers in Brussels.

The activist news agency HRANA said 341 protesters had been killed in the unrest, including 52 minors.

It said 39 members of the security forces were killed and more than 15,820 people had been arrested as of yesterday in protests around 140 cities and towns and 138 universities.

Iranian leaders, who have blamed foreign enemies including the United States for what they call riots, are battling protests bringing together all layers of society, from lawyers to shopkeepers to actors and athletes.

Iran's judiciary said one person had been sentenced to death for "waging war against God", which is punishable by death in Iran, for setting fire to a government building. It said he could appeal the verdict.