Dozens of young British women are using social media to boast of joining the Islamic State's terrifying all-female police force – claiming to be doling out savage beatings, punishment lashings, ordering executions and managing brothels where thousands of Yazidi sex slaves are imprisoned and raped daily after being sold for as little as £27.

Britons including privately-educated Glaswegian Aqsa Mahmood, 20, and Lewisham-born Khadijah Dare, 22, are understood to have joined the Al-Khansa Brigade in ISIS' Syrian de facto capital Raqqa, helping to patrol the city with guns and daggers hidden beneath their religious robes.

The group, which is largely made-up of educated Western women, operates as an ultra-oppressive police force monitoring the behaviour of females in Raqqa - meting out brutal punishments to anyone wearing shoes that aren't black, or those wearing veils made from the wrong material.

Police force: Dozens of Britons are understood to have joined the Al-Khansa Brigade in ISIS' Syrian de facto capital Raqqa, helping to patrol the city with guns and daggers hidden beneath their religious robes

Sick: One woman notorious for the references to the Al Khansa Brigade is British national Umm Farriss, who also calls herself Umm Anwar. She recently mockingly described an encounter with a Yazidi sex slave

Thanks to the head-to-toe niqabs all women living in ISIS-held territory are forced to wear, the Al-Khansa Brigade also acts as a Stasi-esque secret police force - with members covertly spying on men suspected of wrongdoing, before reporting them to ISIS' feared Hisbah religious authority.

Although the figures are impossible to independently verify, the Terrorism Research and Analysis Consortium (TRAC) believes as many as 60 British nationals are currently members of Al-Khansa.

Chief among them is 20-year-old Aqsa Mahmood - was reported missing by her parents a year ago before surfacing in Syria in February as an outspoken supporter of the terrorist group.

Adopting the nom de guerre Umm Layth, which translates as 'mother of Layth', Mahmood was studying diagnostic radiography at Glasgow Caledonian University before leaving the West behind.

Shortly after marrying an ISIS fighter in Raqqa, she is understood to have joined the city's Al-Khansa Brigade - helping to carry out the group's shocking oppression of local citizens, particularly women.

Among the rules she helps enforce are the strict requirement that all women are accompanied by a male chaperone, and that they must wear 'acceptable' clothing when in public.

The strict dress code requires all females to wear nothing by black, including their shoes, and cover every inch of their body, including wearing gloves to cover their hands and fingers.

'We have established the brigade to raise awareness of our religion among women, and to punish women who do not abide by the law,' Raqqa-based ISIS official Abu Ahmad revealed in July.

'There are only women in this brigade, and we have given them their own facilities to prevent the mixture of men and women,' he added.

Terror: Chief among the Britons suspected of being members of the Al-Khansa Brigade is 20-year-old Aqsa Mahmood. She was reported missing by her parents a year ago before surfacing in Syria in February

Everyday life: Adopting the nom de guerre Umm Layth, which translates as 'mother of Layth', Mahmood's former Twitter profile picture appeared to show members of the Al-Khansa Brigade in Raqqa

Shocking: Earlier this year Aqsa Mahmood posted this photograph of her holding the severed head of a Syrian man executed for criminal acts in Syria. She was standing alongside young children at the time

The Al-Khansa Brigade takes its name from a 7th Century poet and contemporary of the Prophet Mohammad whose four sons all died at the Battle of al-Qādisiyyah. Literally translated from classical Arabic, the name Al-Khansa reportedly means 'mother of many martyrs'.

Members of the Al-Khansa Brigade are reportedly paid a monthly salary of £100 and, thanks to them wearing full niqabs covering every inch of skin, operate quite literally under cover.

Not being able to identify who is an ordinary citizen and who is a member of the secret police force has made Al-Khansa one of the most effective elements of ISIS campaign of brutal oppression inside its de facto capital city Raqqa.

In September Abu Ibrahim Raqqawi, a member of the city's anti-ISIS activist group Raqqa is Being Slaughtered Silently, told VICE News: 'The most difficult thing for us, is the Al-Khansa Brigade...I don't know who's from Al-Khansa and who isn't. So when I get out my cell phone and I am taking photos of the city I don't know if any of them are looking at me or not.'

'If you are taking photos and one of the women from Al-Khansa is looking at you, they will catch you immediately, and you'll be executed immediately. This is a big problem for us,' he added.

Abu Ibrahim described how the majority of women in Al-Khansa are foreigners 'from the UK, from the U.S, Dutch, Chechen.' He added that even though many of them can only speak a few words of Arabic, their reputation is such that men and women alike fear their presence.

Another Briton believed to be involved with the Al Khansa Brigade is Lewisham-born Khadijah Dare. Here she is pictured alongside her Swedish terrorist husband Abu Bakr. Their marriage was arranged by his mother

Grim: Two years ago, Dare (pictured left alongside a female jihadi friend named Umm Haditha) left her 'comfortable life' in Britain, where she was known for her dimples and her love of her mother's home cooking

'Terror twins': Zahra (left) and Salma (right) Halane, who have 28 GCSE's between them, are also believed to have been joined the Al Khansa. The 16-year-olds ran away from their Manchester home on 26 June

Inside the Islamic State: The leader of Al-Khansa is believed to be a six foot tall woman named Umm Hamza, who carries a gun, electric cattle-prod and daggers beneath her religious gowns

Another Briton believed to be involved with the Al Khansa Brigade is Lewisham-born Khadijah Dare.

Two years ago, Dare swapped her 'comfortable life' in Britain, where she was known for her dimples and her love of her mother's home cooking, for the horror of Syria.

Now, after appearing in an ISIS recruitment video calling on British Muslims to 'stop being selfish' and give up their families and studies to join the front line in the Middle East, Dare - a pseudonym - is said to be top of MI6's list.

This morning a woman calling herself Umm Waqqas described the Al Khansa Brigade as 'police women'

A security source said: 'Her notoriety has evolved so rapidly that she has achieved a celebrity-like status among jihadists fighting in Syria and those who are thinking of travelling abroad to join ISIS.

Following the sickening murder of James Foley by the militant known as Jihadi John earlier this year, Dare took to Twitter to celebrate the killing. She later confessed her desire to become the first woman to behead a Western hostage in one of ISIS' infamous filmed executions.

Other Britions believed to have been joined the Al Khansa Brigade include the Manchester-born 'terror twins' Zahra and Salma Halane, who have 28 GCSE's between them.

The 16-year-olds left their Manchester home on 26 June to join the conflict, were split up upon arrival, and subsequently sent off to different parts of Syria to marry Islamic State fighters.

At least one of them is now understood to be in Raqqa and reportedly working for Al Khansa.

Earlier this month it emerged that the girls' Somali-born father Ibrahim, 52, and mother Khadra Jama, 45, travelled to Syria to try and rescue their daughters.

Their mother was temporarily held captive by ISIS during the visit and when she eventually did get to meet with one of the girls who simply told her she did not want to return to Britain as she had been chosen by Allah to fight for the Islamic State.

A picture tweeted by Aqsa Mahmood, who goes by the name of @UmmLayt, purports to show her posing alongside women using the nom de guerre's Umm Haritha, and Umm Ubaydah in the Syrian city of Raqqa

Another woman notorious for references to the Al Khansa Brigade is British national Umm Farriss (pictured), who also calls herself Umm Anwar. She uploaded this photograph of herself to Twitter earlier this year

The true identity of several other women connected with the secret police force is not known, but at least two other women claiming to be Britons have made insider reference to Al Khansa.

On Wednesday morning, a woman calling herself Umm Waqqas described the group as 'police women'.

She said they 'roam the streets with their abayas (black cloaks), niqabs and kalashs (assault rifles).'

Another woman notorious for the references to the Al Khansa Brigade is British national Umm Farriss, who also calls herself Umm Anwar.

Earlier this year she described a chilling encounter with a Yazidi 'slave girl'. Umm Farriss claims she entered a building in the city of Raqqa and greeted the entire room. She then described in sickeningly mocking tones how the abused Yazidi woman offered a 'salam' (hello) in response.

Although her Western identity has not yet been established, Umm Farris is believed to have arrived in Syria in February and is known to have posted photographs of her posing with a suicide bomb belt on Twitter before her account was eventually disabled.

Such bravado is not uncommon among young ISIS sympathisers active on Twitter. Some doubt the truth behind their bold claims.

Charlie Winter, programs officer at the think tank Quilliam told MailOnline: 'A lot of the young women out there talk up their role. A lot of them exaggerate the amount on knowledge they are party to.'

'It's all about projecting and exaggerating and that's reflective of the wider Islamic State media operation. There are a lot of people in Syria who claim they are senior than they are, more central to Islamic State operations than they are simply because they are trying to justify why they're there.'

The Al Khansa Brigade which is largely made-up of educated Western women, operates as an ultra-oppressive police force monitoring the behaviour of females in Raqqa - doling out brutal punishments to anyone wearing shoes that aren't black, or those wearing veils made from the wrong material

The true identity of several other women connected with the secret police force is not known, but at least two other women claiming to be Britons have made insider reference to Al Khansa. This morning a woman calling herself Umm Waqqas described the group as 'police women'

Threat: Umm Waqqa added that Al Khan 'roam the streets with their 'niqabs and kalashs (assault rifles)'

The leader of Al-Khansa is believed to be a six foot tall woman named Umm Hamza, who carries a gun, electric cattle-prod and daggers beneath her religious gowns.

Nicknamed 'The Slaughterer', Umm Hamza is understood to have previously been responsible for carrying out lashings and other punishments at Raqqa's women's prison.

Umm Hamza's brutality is said to be notorious throughout the city and her imposing physical presence makes her unmistakable, even though she is never seen in public without her niqab.

Witnesses say she arrived in Raqqa in late 2013 wearing the sort of Niqab popular in Pakistan.

Speaking of Umm Hamza last month, a 25-year-old woman called 'Khadija' who managed to escape ISIS-held Raqqa told CNN: 'She's not a normal female. She's huge, she has an AK, a pistol, a whip, a dagger and she wears the niqab.'

THE PRICE OF HUMAN MISERY - THE FULL ISIS PRICE LIST FOR SLAVES A woman aged 40 to 50 - 50,000 dinars (£27) A woman aged 30 to 40 - 75,000 dinars (£40) A woman aged 20 to 30 - 100,000 dinars (£53) A girl, aged 10 to 20 - 150,000 dinars (£80) A child under nine - 200,000 dinars (£106) Advertisement

Such was Khadija's visible fear that another commander Umm Rayan later sought her out to tell her not to be afraid and that: 'We are harsh with the infidels, but merciful among ourselves.'

ISIS has attempted to justify the keeping of sex slaves by claiming that members of the Yazidi religion are devil worshippers - making them worse than so-called 'people of the book' such as Christians and Jews, who can escape imprisonment by paying a monthly tax known as jizyah.

Captured Yazidis - whose belief system mixes elements from a range of religions and whose central figure of worship is a 'Peacock Angel' - are not able to pay their way out of jail, however.

Men and boys are told to convert to Islam or face immediate death, while women and children are often transported to Raqqa, where the Al-Khansa Brigade force them into sex slavery.

Earlier this month a chilling document emerged purporting to show the 'price list' for sex slaves.

According to the document, obtained by website Iraqinews.com, just £27 will fetch a Yazidi or Christian woman aged between 40 and 50. Chillingly, a child between one and nine will fetch four times that.

The document also states that the slavery market has recently taken a downturn, hitting ISIS' war chest.

Armed and dangerous: Members of the Al-Khansa Brigade are reportedly paid a monthly salary of £100 and, thanks to them wearing full niqabs covering every inch of skin, operate quite literally under cover

Guns and children: In September a Syrian woman agreed to carry a hidden camera to film daily life in Raqqa. Her footage shows several gun-wielding French women who had left their home country to join ISIS

One of the most shocking duties reportedly carried out by the Al Khansa Brigade is the management of brothels frequented by male Islamic State fighters in Syria.

The women and children held in these prisons and raped by terrorists several times a day are members of the Yazidi religion.