WARNING: Graphic Content
After being captured by Islamic State, a group of young girls were forced to stand against a wall while men groped their chest.
"If she had breasts then she was OK to rape," said a Yazidi survivor recounting the experience. "If she did not have breasts they kept her there for another three months and came back to see if she had grown in the meantime; whether she was good for raping then."
The young woman revealed she was forced to watch other girls being raped in front of her, before becoming pregnant and trying to throw herself down the stairs to force a miscarriage.
"Even women who had three or more children were raped in front of their children," she told the UK government in 2015. "There are thousands of other girls right at this moment, in Iraq, in Syria, going through the same thing or about to go through the same thing. Nobody is talking about them and nobody is doing anything."
The harrowing experience forms part of a new report by the Henry Jackson Society's Nikita Malik, looking at how sex slavery has become a lucrative and critical trade for terrorist groups like Islamic State, Boko Haram and Al-Shabaab in recent years.
Trafficking Terror, How Modern Slavery and Sexual Violence Fund Terrorism, reveals how sex slavery has fuelled a thriving marketplace for terror groups through ransom payments.
In the past year, IS has earned between $12 million-$38 million in revenue from the disturbing trade, that also helps to cement bonds between fighters and is used as both a reward and punishment.
"Terrorists use sexual violence, including rape, sexual slavery and forced marriage, to bolster recruits, galvanise fighters, and, in the case of Islamist groups, punish kuffar (disbelievers)," Malik writes.
"Propaganda on sexual slavery serves as an incentive for new recruits and foreign fighters, with the promise of wives and sex slaves acting as a 'pull factor'."
"Religious elements are infused into sexual violence practices to skirt around the moral wrongdoing of rape. Forced inseminations, forced pregnancies, and forced conversions are a means to secure 'the next generation of jihadists'."
The comprehensive report shines a light on an underreported trade that occupies a murky area between sexual violence, terrorism and trafficking and can be complicated by the fact those involved can be both perpetrators and victims.
Islamic State's treatment of sex slaves is well defined within the terror group with a special department and 27-page document setting out "rules" for their treatment.
Fighters' wages can be based on the number of children and women they "own", with women reporting being bought, sold and raped by multiple men until they were forced to run away.
Malik's research found the fact that such groups have gained a foothold in deeply conservative and unstable societies has helped make the promise of having a sex slave attractive to young men.
Meanwhile, local laws in Syria, Nigeria, Libya and Iraq mean women are exposed to a "triple vulnerability" from sexual violence, trafficking and terror that leaves them without protection under international law.
"We're speaking about national laws where marital rape is not recognised as rape. Where to this day rapists are let off the hook if they marry their victims," Malik said, adding it also raises the question of what happens to the children born into terror groups.
"Now that these groups are losing their territory, these children have no documentation, besides the documentation that has been given to them by Islamic State - their birth certificates. These are not legitimate documents because it's not a legitimate state. The governments of Iraq and Syria have not been very forthcoming about how they're going to deal with this issue."
Around 5000 Yazidi woman are estimated to have been sold into slavery by Islamic State, while at least 2000 have been taken by Boko Haram, including the famous abduction of 276 Chibok girls.
Malik is now calling to have sexual violence prosecuted as a tactic of terrorism and an international task force established on the subject. UK Labour MP Yvette Cooper said it's vital the links between sexual violence and terror are understood.
"ISIL, Boko Haram and other evil groups are increasingly seeing human trafficking as a possible revenue stream - and we know that terrorists use sexual violence as one of the weapons they use to divide and create fear within communities. It is important this is recognised in the interpretation of terror in our current laws," she said.