Demonstrations have continued for five successive nights, and reached several towns and cities.
Mahsa Amini died in hospital on Friday after spending three days in a coma.
In Sari, north of Tehran, large crowds cheered as women set their hijabs alight in defiant acts of protest.
Ms Amini was arrested in the capital last week by Iran’s morality police, accused of breaking the law requiring women to cover their hair with a hijab, or headscarf, and their arms and legs with loose clothing.
She fell into a coma shortly after collapsing at a detention center.
There were reports that police beat Ms Amini’s head with a baton and banged her head against one of their vehicles, Acting UN High Commissioner for Human Rights Nada al-Nashif said.
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The police have denied that she was mistreated and said she suffered “sudden heart failure”. Ms Amini’s family has said she was fit and healthy.
The 22-year-old was from Kurdistan Province in western Iran, where three people were killed on Monday as security forces opened fire on protesters.
“Mahsa Amini’s tragic death and allegations of torture and ill-treatment must be promptly, impartially and effectively investigated by an independent competent authority, that ensures, in particular, that her family has access to justice and truth,” Ms Nashif said.
Read more: BBC
