Three people were reportedly killed on Monday at protests over the death in custody of Mahsa Amini.
Mahsa Amini, a 22-year-old from the western city of Saqez, who was from Iran's Kurdish minority, died in hospital on Friday after spending three days in a coma.
Acting UN High Commissioner for Human Rights Nada al-Nashif said there were reports that Ms Amini was beaten on the head with a baton by morality police officers and that her head was banged against one of their vehicles. 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".
An aide to Iran's Supreme Leader Ayatollah Ali Khamenei paid a visit to Ms Amini's family on Monday and told them that "all institutions will take action to defend the rights that were violated", state media reported.