Women have been at the forefront of escalating protests in Iran sparked by the death in custody of a woman detained for breaking hijab laws, media reports said.

Crowds cheered when women burned their hijabs on a bonfire in Sari on Tuesday, the fifth successive day of unrest, BBC reported.

Activists said a woman was among three protesters shot dead by security forces in Urmia, Piranshahr and Kermanshah. The authorities accused protesters of killing two civilians in Kermanshah as well as a police assistant in Shiraz, the report said.

At least seven people are now reported to have been killed since the protests against the hijab laws and morality police erupted after Mahsa Amini’s death.

The 22-year-old Kurdish woman from the north-western city of Saqez died in hospital on Friday, after being in coma for three days.

She was with her brother in Tehran when she was arrested by morality police, who accused her 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 coma shortly after collapsing at a detention centre.

There were reports that police hit Amini on the head with a baton and banged her head against one of their vehicles, acting UN High Commissioner for Human Rights Nada al-Nashif said, BBC reported.

The police have denied that she was mistreated and said she suffered “sudden heart failure”. But her family has said she was fit and healthy.

“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,” Nashif said.

She noted that the UN had received “numerous, and verified, videos of violent treatment of women” as morality police expanded their street patrols in recent months to crack down on those perceived to be wearing “loose hijab”, BBC reported.

“The authorities must stop targeting, harassing, and detaining women who do not abide by the hijab rules,” she added, calling for their repeal.

An aide to Iran’s Supreme Leader Ayatollah Ali Khamenei paid a visit to Amini’s family on Monday and told them that “all institutions will take action to defend the rights that were violated”, state media reported.