A 14-year-old girl was beaten and detained by Iran's 'morality police' for wearing ripped jeans.

The girl, who has not been named, was celebrating her birthday with friends when they were hauled into a police van in the city of Shiraz, in south-west Iran.

Male officers forced the girls into the vehicle having threatened them with pepper spray.

Once inside, female officers attacked them and pulled their hair.

The girls were only set free after signing written pledges saying they would not wear the ripped trousers again and follow the country's strict dress code.

A 14-year-old girl in the city of Shiraz, in Iran, was beaten by the country's 'morality' police for wearing ripped jeans

Recalling the incident, the teenage girl told the Independent: 'There were two women and two men in a huge van and they pushed us into it with the force of their beatings.

'Their objection was to the ripped jeans that we were wearing. There were really no other issues concerning my friends and I.'

The girl's mother told the website: 'It was unbelievable. When I entered the room, they were saying that these girls are not children any more and should wear proper clothes.

'Signs of bruises are still visible all over her body. My daughter and her friends were wearing ordinary clothes...it was just that they were wearing ripped jeans.'

Iran enforces a strict dress code. Since the Islamic revolution of 1979, women have been required the wear the headscarf in public places.

Rules are enforced by thousands of undercover 'morality police', who patrol the streets looking for offenders.

Last year, it was revealed women in Iran were cutting their hair short and dressing as men to avoid the harsh morality police.

At the same time, police arrested eight models as part of a crackdown that targeted 'un-Islamic acts' such as women exposing their hair.

Iranians attempting to resist the patrols created a phone app called 'Gershad' to report their locations last year, but authorities in Tehran responded by deploying a new unit of 7,000 officers.

Homosexuality, adultery and sex outside of marriage are also against Iranian law and can carry the death penalty, while access to Western women's magazines and films is strictly controlled.

Alcohol is also strictly forbidden, with exceptions covering religious minorities but not foreigners.