"If you come and sit with the girls you will find different stories from girl to girl. A lot of them have been sold to Isis fighters, they have been raped in ... public, and by more than two or three people at a time," he told the International Business Times. "They were tortured, beaten and subject to any type of violence."
Other Yazidi survivors have also given disturbing accounts of their treatment by Isis, with one women describing how militants were forcing hostages to give their blood for transfusions.
The atrocities endured by Yazidi sex slaves was exposed more fully in an 87-page report released by Amnesty International in November 2014, which found girls and women were repeatedly raped and sold as sex slaves.
The report found that even children were being sold to Isis fighters or given as "gifts".
Isis considers Yazidis heretical and published an article in its propaganda magazine Dabiq attempting to justify the practice of selling them using theological rulings of early Islam.
However, experts say the practice has caused friction among the ranks of the extremist group. Sajad Jiyad, Research Fellow and Associate Member at the Iraqi Institute for Economic Reform, told the Independent that many supporters had been in denial about the trafficking of kidnapped Yazidi women until the Dabiq article was published.
The Yazidis
• Religious sect found in northern Iraq, Syria and the Caucasus
• Religion incorporates elements of many faiths, including Zoroastrianism
• Principal divine figure, Malak Taus (Peacock Angel), is the supreme angel of the seven angels who ruled the universe after God created it
• Many Muslims and other groups incorrectly view Yazidis as devil worshippers
• There are estimated to be around 500,000 Yazidis worldwide