Yazidi women enslaved by ISIS are being sold for as little as $10, according to an activist who has interviewed a number of those who have fled captivity.

Khider Domle told NBC news that women are often traded between militants a number of times, and used to demand ransom sums from their families. "Some are sold for weapons, or for just $10, or 10 cigarettes," he said.

A 23-year-old woman identified as Aveen (not her real name) told NBC news that she was abducted by ISIS fighters when her village in Iraq's Sinjar province was attacked in August 2014. Militants took girls as young as seven years old and held them in a school, from where they were taken to be raped and used as sex slaves.

Aveen escaped after nearly a year in captivity, and was beaten and raped numerous times.

Another Yazidi woman whose granddaughters are still being held by ISIS wept as she was interviewed. "I pray for this hell to end," she said.

It is thought that around 2,000 Yazidi women are currently being held captive by jihadists. Earlier this year the UN said that ISIS may have committed genocide against the minority group, a claim which was later backed up by the US Holocaust Memorial Museum.

Yazidism is an offshoot of Zoroastrianism, which blends ancient religious traditions with both Christianity and Islam. ISIS believes them to be "devil-worshippers".

Harrowing accounts of treatment at the hands of ISIS militants have emerged from women who have managed to escape. A 22-year-old Yazidi told CNN in October that she was raped by 12 militants while in captivity, who believed that a woman would become Muslim if she was raped by at least ten men.

ISIS last year issued guidelines specifying how its followers were to treat their female slaves.

Dated October/November 2014, the Q&A leaflet detailed exactly how they may buy, sell and abuse "unbelieving" women – thought to mean all those who are not Sunni Muslims.

It clarified that "It is permissible to have intercourse with the female slave who hasn't reached puberty if she is fit for intercourse," and any female slave who attempts to run away is to be "reprimanded in a way that deters others like her from escaping".

There are also concerns regarding the way that women who have fled ISIS captivity are able to integrate back into their home communities. An Amnesty International report this year found that they often face stigmatisation, and struggle to find husbands, reportedly leading some doctors to perform operations to reverse the loss of virginity.