The Sunni jihadist group Islamic State in Iraq and Syria (ISIS) has made rape a central part of worship and justified the practice of forcing Yazidi women and girls into sexual slavery on the name of Koran, a report said Friday.

A 12-year-old Yazidi rape victim, said in an interview with Rukmini Callimachi of The New York Times that her attacker maintained that raping her was not sinful because the Quran "condones and encourages" attacking non-Muslim women.

"I kept telling him it hurts - please stop," the 12-year-old girl said in the interview, which was held at a refugee camp in Iraq's Qadiya.

"He told me that according to Islam he is allowed to rape an unbeliever. He said that by raping me, he is drawing closer to God," she said.

"Every time that he came to rape me, he would pray. He kept telling me this is ibadah (worship)," another rape victim, 15, told award-winning journalist Callimachi.

Nearly 5,000 Yazidi women and girls remain in captivity of ISIS, which controls parts of Syria and Iraq and established self-claimed Caliphate in Raqqa, according to the Daily Mail.

The extremist group is engaged in open trading of captured Yazidi women, forcing them into sexual slavery.

"The extremist group launched its large-scale attack on Yezidi communities around Sinjar. The group killed thousands of Yezidi civilians, and seized and sold off Yezidi women for their fighters' sexual gratification," Human Rights Watch said a statement recently.

Yadizi female sex slaves aged 40-50 can fetch a low price of $43, while females aged 1-9 are priced at a relatively higher amount of $172, HNGN previously reported. The brutal terror outfit has recently executed 19 Yadizi women for refusing to be part of sex jihad.