Horror stories of sexual brutality against teenage girls continue to emerge from Iraq and Syria as UN officials hear firsthand accounts of what has been transpiring under the Islamic State (ISIS/ISIL/IS) reign of terror.

The UN envoy on sexual violence, Zainab Bangura, recently completed a fact-finding mission on sexual violence in Iraq and Syria, where she spoke with women and girls who had escaped from Islamic State captivity, as well as visiting refugees in Turkey, Lebanon, and Jordan.

Bangura’s descriptions of the ISIS slave trade in young girls are particularly gruesome. In an interview Monday, she said that young girls are routinely abducted by Islamic State fighters in Iraq and Syria and then sold in slave markets “for as little as a pack of cigarettes.”

A report from Human Rights Watch found “systematic sexual crimes” had been carried out against women and girls, and Bangura has said that some are sold naked in cities such as Raqqa and Mosul.

Many of the kidnapped girls are part of the Yazidi, Christian, or Turkmen Shia minorities targeted by the Islamic State militants.

According to Bangura, when IS militants take over a village, they separate men and women and immediately execute all men and boys aged 14 and over. The women are divided by age, and “the girls are stripped naked, tested for virginity and examined for breast size and prettiness,” she said.

The youngest, prettiest virgins command higher prices and are sent off to Raqqa, the IS stronghold.

Bangura said there is a hierarchy, with sheikhs getting first choice, then emirs, then fighters.

“They often take three or four girls each and keep them for a month or so, until they grow tired of a girl, when she goes back to market. At slave auctions, buyers haggle fiercely, driving down prices by disparaging girls as flat-chested or unattractive,” she said.

Bangura spoke of a specific case where a group of more than 100 girls were locked up in a room of a small house. The girls were “stripped naked and washed,” then made to stand in front of a group of men who decided “what you are worth.”

She said that one 15-year-old girl was sold to an ISIS leader, a sheikh, who showed her a gun and a stick and said, “Tell me what you want.”

“She said ‘the gun,’ and he replied: ‘I didn’t buy you so that you could kill yourself,’” then proceeded to rape her, Bangura said.

She also heard of “a 20-year-old girl who was burned alive because she refused to perform an extreme sex act.”

Abducting girls has become an integral part of the ISIS strategy to recruit foreign fighters, who have been arriving in Iraq and Syria in record numbers over the past year and a half.

“This is how they attract young men – we have women waiting for you, virgins that you can marry,” Bangura said. “The foreign fighters are the backbone of the fighting.”

“This is a war that is being fought on the bodies of women,” Bangura said.

A UN technical team is slated to travel to the region soon to formulate a detailed plan to help victims of jihadist sexual violence.

Follow Thomas D. Williams on Twitter @tdwilliamsrome.