Hundreds of Yazidi women being held prisoner by Islamic State fighters in Iraq are being sold off as brides for as little as $25 or repeatedly raped if they refuse, it has been claimed.

Survivors have told how beauticians were brought in to put makeup on the women before they were attacked, and said some victims were forced to call their families after to explain what had happened.

According to those who escaped Badush Prison, in Mosul, northern Iraq, the number of women held there could be in the thousands and include Christians and Turkomens - a largely Muslim group closely related to the Turks.

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Survivors of Badush Prison, in Mosul, northern Iraq, have said women arriving there are given two choices: convert to Islam and be sold as a bride, or refuse and be raped (file pic)

While most Yazidi women fleeing Mount Sinjar are now in refugee camps such as this one, hundreds are said to be being held by IS in Mosul

Following the capture of Mosul by IS (formerly known as ISIS or ISIL) in June, troops stormed the prison, took 670 Shia inmates from their cells, and executed them inside the compound.

Since then the jail has been used to house women captured by the Islamic militants during their campaign across Iraq, including many Yazidis who failed to escape from Mount Sinjar.

Nearly half a million Yazidis, a minority religious sect, were displaced after IS militants overran their ancestral home of Sinjar and began executing people for being devil worshippers.

According to Pakhshan Zangana, an official in The Kurdish Regional Government, women arriving at the jail are given two choices: convert to Islam and be sold off for between $25 and $150, or refuse and be subjected to rape and slow death.

She told The Daily Beast that one girl called her mother from inside the jail and described being raped by dozens of men in the space of just a few hours.

Others have told how some women have given birth inside the jail, only to have the babies taken away hours later, never to see them again. Some of the victims are as young as 14.

Zangana is now trying to raise money to buy the girls back, but without international aid she has been forced to turn to crowd-sourcing, promising people their money back if they help.

Hundreds of Yazidis are still fleeing Mount Sinjar (pictured) and are at risk of being captured by IS

Some escaped prisoners have said that IS fighters ordered beauticians to come and put makeup on the women before they were either attacked or sold to new husbands

She said: 'It’s complete psychological warfare. These families are already destroyed by the loss of their loved one’s, and now ISIS has them calling to tell them of the atrocities they have suffered.'

She added that the crisis did not just affect Iraq or the Yazidis, but was caused by international fighters joining IS from Chechnya in Russia, Britain and Holland.

Meanwhile, across the border in Syria, IS today posted a graphic video which apparently showed Islamist soldiers executing around 250 Syrian troops.

An Islamic State fighter claimed the men were from the Syrian government's Tabqa air base which extremists seized on Sunday, potentially handing them warplanes, tanks, artillery and ammunition.

The airfield was the last government-controlled base in the Raqqa region, which is now solely under the control of IS fighters.

Human Rights Watch described shocking video as evidence of 'another ISIS war crime'.

US airstrikes in Iraq have helped to stop the IS advance across the country for now, but jihadi fighters have also managed to repel government attempts at a counter attack.