The United Nations on Tuesday named three women to lead a rights investigation into Iran's violent crackdown on women-led protests that have rocked the Islamic republic for more than three months.

Bangladesh Supreme Court lawyer Sara Hossain, Pakistani law professor Shaheen Sardar Ali and rights activist Viviana Krsticevic from Argentina will be the independent members of the fact-finding mission, UN Human Rights Council head Federico Villegas announced.

Hossain, a long-time human rights activist, will chair the investigation, the council presidency added.

Iran is highly unlikely to allow the trio to enter the country and carry out their mission, with Tehran fiercely opposing the creation of the international investigation that 47 rights council members voted for last month.

The three women will document the Iranian authorities' repression of the protests and potential human rights violations with a view to possible legal action against officials in Iran or elsewhere.

Mass demonstrations, unprecedented since the 1979 Islamic revolution, have swept across the country since September after the death in custody of Iranian-Kurdish woman Mahsa Amini, leading to violent and sometimes deadly clashes with security forces.

The 22-year-old had been arrested by Iran's notorious morality police for allegedly flouting strict rules on correctly wearing the Islamic headscarf, triggering nationwide unrest in favour of women's rights.

The authorities have executed some protesters and condemned others to capital punishment for involvement in what they describe as riots encouraged by arch-foes Israel and the United States.

Human rights organisations say legal procedures have been rushed and confessions obtained under torture.

The United Nations estimates that around 14,000 people have been arrested since mid-September, while Oslo-based NGO Iran Human Rights says 469 protesters have been killed.