Iran’s supreme leader on Monday gave his full backing to security forces confronting protests ignited by the death of Mahsa Amini in custody, comments that could herald a harsher crackdown to quell unrest more than two weeks since she died.

In his first remarks addressing the 22-year-old woman’s death after being arrested for wearing clothes deemed un-Islamic, Ayatollah Ali Khamenei said her death “deeply broke my heart” and called it a “bitter incident” provoked by Iran’s enemies.

“The duty of our security forces, including police, is to ensure the safety of the Iranian nation... The ones who attack the police are leaving Iranian citizens defenceless against thugs, robbers and extortionists,” Khamenei said.

Security forces, including police and the volunteer Basij militia, have been leading a crackdown on the protests, with thousands arrested and hundreds injured, according to rights groups, which put the death toll at over 130.

Iranian authorities have reported many members of the security forces killed during the unrest, which has spiralled into the biggest show of opposition to Iran’s authorities in years, with many calling for the end of more than four decades of Islamic clerical rule.

Khamenei said security forces had faced “injustice” during the protests. “In recent incidents, it is above all security forces, including the police and Basij, as well as the people of Iran, who were wronged,” he said.

“Some people have caused insecurity in the streets,” Khamenei said, condemning what he described as planned “riots”, and accusing the United States and Israel — the Islamic Republic's arch-adversaries — of orchestrating the disturbances.

Amini, whose funeral in the Kurdish town of Saqez on September 17 sparked the unrest that quickly spread across Iran, died after being taken into the custody of Iran’s morality police in the capital Tehran over “inappropriate attire”.

The protests have not abated despite a growing death toll and an increasingly violent crackdown by security forces using tear gas, clubs and — in some cases, according to videos on social media and rights groups — live ammunition.

Protests continued across Iran on Monday, with university students staging strikes after security forces clashed with students at a prominent Tehran university on Sunday.

Dozens of students were arrested and many have been injured according to social media posts and videos. Reuters could not verify the videos and posts.