Iranian authorities are subjecting women to widespread surveillance to enforce the obligatory headscarf, even inside cars, and then imposing punishments including the confiscation of vehicles, Amnesty International said on Wednesday.

The Islamic republic's leadership was in 2022 shaken by mass protests that saw women denounce the dress code but has made clear it has no plan to abandon the obligatory hijab imposed after the 1979 Islamic Revolution.

Amnesty said in a report, based on testimony from over 40 women inside Iran published ahead of the March 8 International Women's Day, that women were being targeted with "widespread surveillance" in public spaces and "mass police checks" targeting women drivers.

It said pictures captured by surveillance cameras or reports from plain clothes agents using police app Nazer identify licence plates of vehicles with female drivers or passengers deemed to have violated the rule.

The women then receive text messages ordering them to report to the police and hand over the vehicles as punishment. It said hundreds of thousands of such orders to impound vehicles have been issued.

The cars can then be released in some cases after 15-30 days once "arbitrary" fees are transferred and written pledges obtained to observe compulsory veiling.

"In a sinister attempt to wear down resistance to compulsory veiling... Iran's authorities are terrorising women and girls by subjecting them to constant surveillance and policing," said Diana Eltahawy, Amnesty's deputy director for the Middle East and North Africa, denouncing "draconian tactics".

It said authorities have also conducted mass random checks, with police pulling over the women drivers to check if their cars are to be confiscated.

Access to transport, airports and banking services is regularly denied and made conditional upon women wearing a headscarf, Amnesty said.

Those defying the rule face prosecution and in January 2024 a flogging sentence of 74 lashes was implemented against a young woman, Roya Heshmati, for appearing unveiled in public.

Protests erupted in September 2022 following the death in police custody of Mahsa Amini, who had been arrested for allegedly violating the hijab rule.

The demonstrations subsided in the face of a crackdown that saw hundreds killed and thousands arrested.

Iran's parliament in September 2023 passed the "Bill to Support the Culture of Chastity and Hijab" which increases punishments for those deemed to have violated the rule.

It now awaits approval from the Guardians Council supervision body.