An Iranian woman who was filmed waving a hijab from a pillar box in Tehran has gone missing, sparking fears that she may have been arrested.

A video of the unidentified woman waving a white headscarf on a stick was widely shared on social media at the end of December.

She appeared to be protesting against Iran's restrictive dress code for women.

Since the Iranian revolution in 1979, women have to cover their hair in public to avoid punishment.

In recent years, women have started demonstrating against the strict dress code by sharing images of themselves with their hair uncovered on social media, tagged #whitewednesdays.

The woman in the video was not wearing her headscarf. She had tied it to a stick in an apparent reference to the White Wednesday protests against Iran's strict interpretation of Islamic law on female modesty.

She is thought to have staged the protest on 27 December, a day before violent demonstrations against rising fuel and food prices broke out across the country.

But she has reportedly not been seen since.

Renowned human rights lawyer Nasrin Sotoudeh told AFP that she had been arrested. The lawyer discovered from neighbours that the missing woman is 31 years old and has a 19-month-old baby.

"The witnesses on the scene who saw her being taken away and even accompanied her to the police station gave me this information. I have no contact with her family," she said.

Sotoudeh said the protest showed someone who was "at the end of their tether because of all the controls placed on her body over the 31 years of her life".

"Women feel they have no control over their bodies. It is a prelude to infringing all their rights," she added.

The protest took place on the same day that Tehran's police chief said that officers would take a softer approach to women who did not follow the strict clothing rules.

Brigadier General Hossein Rahimi said: "According to a decision of the commander of the police force, those who do not observe Islamic codes will no longer be taken to detention centres nor [have] judicial files opened on them."

Rahimi's comments marked a stark shift from police protocol under his predecessor, General Hossein Sajedinia, who announced in April 2016 that undercover 'morality' police would be installed to report on "bad hijab" cases, where women were not wearing their headscarf in line with Islamic rules.

People have shared the image of the missing woman along with the hashtag '#Where_is_She?' and demanded that Iranian officials release information about her whereabouts.