Iran's supreme leader Ayatollah Ali Khamenei has said the death of Mahsa Amini "deeply broke my heart".
Speaking at a military ceremony on Monday, Mr Khamenei described the 22-year-old woman's death in custody as a "bitter incident".
Ms Amini died after being arrested by Iran's morality police for allegedly breaking the country's strict Islamic dress code. Her family have claimed she was tortured.
'Not ordinary Iranians'
After some of the biggest protests in years broke out as a result, the supreme leader blamed the riots on "the United States and the Zionist regime".
He said they were "planned" by people who are "not ordinary Iranians", adding that the security forces policing them have faced "injustice".
"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," he said.
Dozens dead since protests broke out
Protesters have taken to the streets across 31 Iranian provinces - and other countries including Turkey, Lebanon, and France - in defiance of the Islamic republic's treatment of women.
They have played a dominant role in the demonstrations, publicly cutting their hair, removing and burning their veils.
Iranian state TV claims 41 demonstrators have died since protests began on 17 September, but Norway-based group Iran Human Rights estimates the figure to be much higher at 133.
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A 23-year-old TikTok star named Hadis Najafi was among those shot dead.
Mobile phone footage from near Tehran's prominent Sharif University shows security forces using tear gas and people trying to escape gunfire.
Speaking on Sunday, Iran's parliamentary speaker Mohammad Bagher Qalibaf warned that the protests could destabilise the country.
The country's hard-line president Ebrahim Raisi has ordered an investigation into Ms Amini's death and threatened to crack down on those causing unrest.
He has previously blamed foreign powers for the protests, claiming last week that foreign nationals were among those arrested in connection with them.
What happened to Mahsa Amini?
Ms Amini was arrested on 13 September for wearing her hijab too loosely, which is deemed as "unsuitable attire" under Iran's Islamic dress code.
She died three days later in hospital after falling into a coma.
While details of her post-mortem have not been released, her family have said she was "tortured" and claims a report from the hospital shows she "suffered a concussion from a blow to the head".
Iranian police claim Ms Amini died of a heart attack and deny she was beaten to death in custody.
Independent experts affiliated with the United Nations say reports suggested she was severely beaten by the morality police, without offering evidence.