Iran's supreme leader has accused the United States and Israel of masterminding the protests triggered by the death of a woman who was arrested over how she wore her headscarf, or hijab.

In a speech on Monday, Ayatollah Ali Khamenei broke his silence on the ongoing sporadic protests, which started after 22-year-old Mahsa Amini died last month while in custody. Protesters believe she was beaten by police.

Khamenei said he was heartbroken by her death. But he described scenes of protesters setting fire to banks and cars as unusual. He asserted that the unrest was orchestrated by the US and Israel.

Khamenei expressed support for the crackdown by judicial authorities on protesters. He said those who engage in sabotage should be punished accordingly.

The latest unrest has been characterized by a spate of clashes between protesters and security forces, mainly on university campuses across the country.

State-run media said 41 people have died so far. Human rights activists say the figure understates the true death toll. Observers fear a further crackdown could result in more casualties.