The independent and Oslo-based human rights group Iran Human Rights said on Friday that more than 50 people had been killed so far.
The widespread protests erupted after 22-year-old Mahsa Amini, who was arrested by the Islamic dictatorship's hard-line morality police, died in custody last week.
Her suspected crime was not wearing the obligatory veil properly.
Iranian President Ebrahim Raisi has promised a swift investigation, but the protests quickly spread to dozens of cities and have continued for several days.
In connection with the Friday prayer, demonstrations in support of the government were also arranged in several places.