"Telegram is extremely popular in the Middle East, among other regions," said Telegram spokesman Markus Ra.
"This, unfortunately, includes the more marginal elements and the broadest law-abiding masses alike." He added the company is committed to prevent abuse of the service and that it routinely removes public channels used by IS.
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"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," said Matt Steinfeld, a spokesman for Whats App.
"Even if I had lost both eyes, it would have been worth it, because I have survived them." Human traffickers are using Uber to smuggle migrants The Sunni extremists view the Yazidis as barely human. The activist showed AP the negotiations for the captives in encrypted conversations as they were occurring in real time.
The Yazidi faith combines elements of Islam, Christianity and Zoroastrianism, an ancient Persian religion. The postings appear primarily on Telegram and on Facebook and Whats App to a lesser degree, he said.
In the images obtained by AP, many of the women and girls are dressed in finery, some in heavy makeup. One of them is Nazdar Murat, who was about 16 when she was abducted two years ago — one of more than two dozen young women taken away by the extremists in a single day in August 2014.
All look directly at the camera, standing in front of overstuffed chairs or brocade curtains in what resembles a shabby hotel ballroom. Her father and uncles were among about 40 people killed when IS took over the Sinjar area, the heart of the Yazidi homeland.
Inside an immaculately kept tent in a displaced persons camp outside the northern Iraqi town of Dahuk, Nazdar's mother said her daughter managed to call once, six months ago. 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.
In addition to the posting for the 12-year-old in a group with hundreds of members, the AP viewed an ad on Whats App for a mother with a 3-year-old and a 7-month old baby, with a price of ,700.
"She wants her owner to sell her," read the posting, followed by a photo.
While the Islamic State group is losing territory in its self-styled caliphate, it is tightening its grip on the estimated 3,000 women and girls held as sex slaves.