The head of Iran's powerful Revolutionary Guards warned protesters that Saturday would be their last day of taking to the streets, in a sign that security forces may intensify their already fierce crackdown on unrest sweeping the country.

Iran has been gripped by protests since the death of 22-year-old Kurdish woman Mahsa Amini in the custody of the morality police last month, posing one of the boldest challenges to the clerical leadership since the 1979 revolution.

"Do not come to the streets! Today is the last day of the riots," Guards commander Hossein Salami said in some of the toughest language used in the crisis, which Iran's clerical leadership blames on its foreign enemies including Israel and the United States.

"This sinister plan, is a plan hatched ... in the White House and the Zionist regime," Salami said. "Don't sell your honour to America and don't slap the security forces who are defending you in the face."

Iranians have defied such warnings throughout the popular revolt in which women have played a prominent role. There were more reports of fresh bloodshed and renewed protests on Saturday.

Human rights group Hengaw reported security forces shooting students at a girls' school in the city of Saqez. In another post, it said security forces opened fire on students at Kurdistan University of Medical Science, in the Kurdistan provincial capital of Sanandaj.

Several students were injured, one of them shot in the head, Hengaw said. Reuters could not verify this report.

PROTESTERS ON TRIAL

The widely feared Revolutionary Guards, an elite force with a track record of crushing dissent which reports directly to Supreme Leader Ayatollah Ali Khamenei, have not been deployed since demonstrations began last month.

But the warning by Salami, who was speaking at a funeral of victims killed in an attack this week claimed by Islamic State, suggests Khamenei could unleash them in the face of relentless demonstrations now focused on toppling the Islamic Republic.

Videos posted on social media by activist groups purported to show protests at a number of universities across the country in cities including Kerman, Mashhad, Qazvin, Ahvaz, Arak, Kermanshah, Yazd and a dozen campuses in the capital, Tehran.

The activist HRANA news agency posted a video which it said showed protests at a university holding hands in a large circle and chanting: "If we don't unite, we will be killed one by one."

HRANA said 272 protesters had been killed in the unrest as of Friday including 39 minors and 34 members of the security forces. Nearly 14,000 people have been arrested in protests in 129 towns and cities and some 115 universities.

A hardline Revolutionary Court began the trials of some of the 315 protesters charged so far in Tehran, at least five of whom are accused of capital offenses, the official news agency IRNA reported.

The defendants include a man accused of hitting and killing a police officer with his car and injuring five others, IRNA said. He is charged with "spreading corruption on earth," an offense punishable by death under Iran's Islamic laws.

Another man is charged with the capital offense of "moharebeh" - an Islamic term meaning warring against God - for allegedly attacking police with a knife and helping set fire to a government building in a town near Tehran, IRNA added.

The court is headed by Abolghassem Salavati, a judge on whom the United States imposed sanctions in 2019 after accusing him of having punished Iranian citizens and dual nationals for exercising their freedoms of speech and assembly.

(Editing by Andrew Cawthorne, Helen Popper and Frances Kerry)