Wednesday’s killing of Shi’ite pilgrims came on the same day that Iranian security forces clashed with increasingly strident protesters marking the 40-day anniversary since the death in police custody of Mahsa Amini, a 22-year-old Kurdish woman.

“Riot police shot mourners who gathered at the cemetery for Mahsa’s memorial ceremony … dozens have been arrested,” the witness said. Iranian authorities were not available to comment.

The semi-official ISNA news agency said about 10,000 people were at the cemetery, adding that the internet was cut off after clashes between security forces and people there.

Videos on social media showed crowds packing streets in many cities and the bazaars of Tehran and some other cities shut down with people chanting “Death to Khamenei”.

1500tasvir, a Twitter account focused on Iran protests with 280,000 followers, reported a “brutal crackdown” on protesters in multiple locations in Tehran, including a gathering at the Tehran Medical Association.

Video footage on social media appeared to show members of the Basij militia shooting at protesters in Tehran.

Other videos showed protesters chasing riot police and throwing stones. They also showed protesters in the holy Shi’ite city of Mashhad setting fire to a riot policeman’s motorbike. In Tehran, a protester hit a policeman, while in the city of Qazvin riot police opened fire on protesters.

Some protesters chanted: “We will fight, we will die, we will get Iran back” from its clerical rulers.

Reuters was not able to verify the authenticity of the footage.

State news agency IRNA said a member of the elite Revolutionary Guards was shot dead “by rioters” in the western city of Malayer.

An Iranian former pro-reform official said the spread of the protests appeared to have taken authorities by surprise and contrasted with the establishment’s assertions that support for the Islamic system is overwhelming.

While some analysts said prospects for the imminent dawn of a new political order are slim, activists said a wall of fear had fallen and the path to a new revolution was not reversible.

Students have played a pivotal role in the protests, with dozens of universities on strike. Hundreds of schoolgirls have joined in, chanting “Freedom, Freedom, Freedom,” despite fierce crackdowns by security forces.

State media and hardline officials have branded protesters “hypocrites, monarchists, thugs and seditionists”.

Rights groups said at least 250 protesters had been killed, including teenage girls, and thousands had been arrested.

The authorities, who have accused the United States and other Western countries of fomenting what they call “riots”, have yet to announce a death toll but state media have said around 30 members of the security forces have been killed.