The posting in Arabic is chilling. A girl for sale: 'Virgin. Beautiful. 12 years old.... Her price has reached $12,500 and she will be sold soon.'

The advertisement, along with others for kittens, tactical gear and weapons, appeared on an encrypted Telegram app and was shared with The Associated Press by an activist with Iraq's persecuted Yazidi community, which is trying to free an estimated 3,000 women and girls still held as sex slaves by ISIS extremists.

As ISIS loses control of one city after another in its self-styled caliphate, it is tightening its grip on its captives, taking the Yazidis deeper into its territory and selling them as chattel on popular encrypted apps such as Telegram and WhatsApp, The Associated Press has found.

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Lamiya Aji Bashar, 18, described how ISIS raided her village abducting her along with her sisters and brothers and passing her around from militant to militant. While making her escape, a mine exploded, killing two girls fleeing with her and leaving the teenager's face scarred and blinding her in one eye

Yazidi woman, Nuri Murat, described how ISIS killed her husband before abducting their daughter who was just 16 at the time

ISIS took this photo of Yazidi girl Nazdar Murat, as part of a database the militants have put together of Yazidi girls and women they have enslaved

The extremists are targeting smugglers who rescue captives for assassination and are deploying a slave database with captives' photos and owners' names to prevent escape through checkpoints.

Thousands of Kurdish-speaking Yazidis were taken prisoner and thousands more were massacred when ISIS fighters overran their northern Iraqi villages in August 2014.

Since then, as the Yazidi captives have been conscripted into sexual slavery, smugglers have managed to free 2,554 women and girls.

But by May, an ISIS crackdown reduced those numbers to just 39 in the last six weeks, according to figures provided by the Kurdistan regional government.

The AP has obtained a batch of 48 head shots of the captives, smuggled out by an escapee. The portraits appear to be the same as those used in a database to prevent the captives from slipping past checkpoints, or for barter and sale on popular apps.

Mirza Danai, founder of the German-Iraqi aid organiSation Luftbrucke Irak, said the slave database documents the captives as if they were property.

Ordeal: Lamiya Aji Bashar, an 18-year-old Yazidi girl, managed to escape her ISIS group enslavers

Barbaric: ISIS regularly offer women and children for sale using mobile telephone apps and have a database of their slaves

'They register every slave, every person under their owner, and therefore if she escapes, every Daesh control or checkpoint, or security force - they know that this girl ... has escaped from this owner,' said Danai, using a common acronym to refer to ISIS.

One of those girls is Lamiya Aji Bashar, who in March made her fifth attempt at escape, running to the border with ISIS fighters in pursuit.

A land mine exploded, and two Yazidi girls who were accompanying her were killed. The bomb left Lamiya blind in her right eye, her face scarred by melted skin.

Speaking from a bed at her uncle's home in the northern Iraqi town of Baadre, the 18-year-told AP that despite being disfigured, she did not regret her perilous escape from her jailers.

'Even if I had lost both eyes, it would have been worth it,' she said, 'because I have survived them.'

The Yazidis have been targeted by ISIS because they practice an ancient faith combining elements of Islam, Christianity and Zoroastrianism, and the Sunni extremists view them as infidels.

The Yazidis' pre-war population in Iraq was estimated at 500,000. Their number today is unknown.

An activist looks at an ISIS marketplace on the encrypted app Telegram, advertising a 12-year-old Yazidi girl as a slave for the price of $12,500

U.S. State Department spokesman John Kirby told the AP that the U.S. continues 'to be appalled by credible reports that Daesh is trafficking in human beings, and sex slavery in particular.'

'This depravity not only speaks to the degree to which Daesh cheapens life and repudiates the Islamic faith, it also strengthens our resolve to defeat them,' he said.

The photos obtained by AP depict girls dressed in finery, some in heavy makeup. They stare somberly at the camera. Some are barely teenagers. Not one looks older than 30.

Nazdar Murat is among them. She was about 16 when she was abducted along with more than two dozen girls and women who fled their home in Iraq's Sinjar area when IS took over.

Inside an immaculate tent outside Dahuk, Nouri Murat, Nazdar's mother, said her daughter managed to call once, six months ago for a few seconds.

Bread crumbs kept by a Yazidi girl while in ISIS captivity, in Dahuk, northern Iraq. Some 2,500 Yazidi women and girls have escaped ISIS slavery through paid smugglers, but the numbers of those reaching freedom is dropping as militants tighten their grip on their sex slaves

An activist documenting ISIS crimes against Yazidis arranges the pages of a diary written by a Yazidi girl while in ISIS militant captivity

'We spoke for a few seconds. She said she was in Mosul,' said Murat, referring to Iraq's second-largest city. 'Every time someone comes back, we ask them what happened to her and no one recognizes her. Some people told me she committed suicide.'

She is not sure whether to believe them.

Hussein Koro al-Qaidi, head of the Yazidi assistance committee in the northern Iraqi city of Dahuk, said no one has stepped up on the Yazidis' behalf. And money to pay for smugglers or ransoms is now running out, according to the Kurdish government and organizations working to save the women and children.

'Neither the Iraqi government, nor the international charities or other countries are helping us to save the Yazidi girls,' said al-Qaidi.

Contraband photos of captives offer families a thread of hope that they might see them again. But they are also used by IS to sell them on Telegram and, to a lesser degree, WhatsApp and Facebook, according to an activist who asked to remain unnamed for fear of his safety.

The activist, showed AP negotiations for the captives in real time on WhatsApp and Telegram, in private chats that cannot be read by outside eyes.

Facebook-owned WhatsApp and Telegram use end-to-end encryption to protect users' privacy.

Both have said they consider protecting private conversations and data paramount, and that they cannot access users' content.

Telegram says it will remove illegal public content 'when deemed appropriate.' WhatsApp can, under its terms of service, ban a phone number if it believes the user has submitted illegal content.

'Telegram is extremely popular in the Middle East, among other regions,' said Telegram spokesman Markus Ra when asked about ISIS use of its app.

The sun sets as women visit a Yazidi shrine overlooking at Kankhe Camp for the internally displaced in Dahuk, northern Iraq

Clothing worn by a Yazidi girl enslaved by ISIS militants, collected by a Yazidi activist to documentcrimes against the community

'This, unfortunately, includes the more marginal elements and the broadest law-abiding masses alike.'

He said the company is committed to prevent abuse and routinely removes public channels used by IS that have been reported by users.

Mark Steinfeld, a spokesman for WhatsApp, said, 'We have zero tolerance for this type of behavior and disable accounts when provided with evidence of activity that violates our terms. We encourage people to use our reporting tools if they encounter this type of behavior.'

The captives' odds of rescue grow slimmer each day.

Even when ISIS retreats from towns like Ramadi or Fallujah, the missing girls are nowhere to be found among the thousands of newly liberated civilians.

Kurdistan's besieged regional government has slowed reimbursement to families who have paid off smugglers or ransom demands, Andrew Slater of the Yazidi advocacy group Yazda said.