A magazine purportedly published by the Islamic State group says that militants have captured, enslaved and sold Yazidi women and children, confirming allegations that have been made against the group for months.

The claim came as Human Rights Watch said Sunday that hundreds of Yazidi men, women and children from Iraq are being held in makeshift detention facilities in Iraq and Syria by the group, commonly known as ISIS.

Tens of thousands of Yazidis fled into the Sinjar Mountains, many getting stranded there for weeks, after the militant onslaught on Sinjar in August, part of the Islamic State group's lightning advance across northern and western Iraq. Hundreds were killed in the attack, and tens of thousands fled for their lives, most to the Kurdish-held parts of northern Iraq.

Iraq's Human Rights Ministry said at the time that hundreds of women were abducted by the militants, who consider the Yazidis, a centuries-old religious minority, a heretical sect. Some also alleged the Islamic State group enslaved and sold Yazidi women and children, though the group itself did not comment on it.

The issue of Dabiq magazine released Sunday stated that "the enslaved Yazidi families are now sold by the Islamic State soldiers." It added that "the Yazidi women and children were then divided according to the Shariah amongst the fighters of the Islamic State who participated in the Sinjar operations."

Most of the Yazidis are now displaced in northern Iraq, many having lost loved ones in their flight to safety. Some say that their women and girls were snatched during the militant raid.

In one section of the magazine, a statement attributed to Mohammed al-Adnani, the spokesman for the Islamic State group, read: "We will conquer your Rome, break your crosses, and enslave your women," addressing those who do not subscribe to its hard-line interpretation of Islam.

The release of the magazine came as New York-based Human Rights Watch said Yazidi men, women and children remain held by the group. Its report noted that the group "separated young women and teenage girls from their families and has forced some of them to marry its fighters."

One woman told Human Rights Watch that she saw Islamic State fighters buying girls, and a teenage girl said a fighter bought her for $1,000, the report said. The Associated Press independently has interviewed a number of Yazidi women and girls who escaped captivity and several claimed that they were sold to Islamic State fighters in Iraq and Syria.

The Associated Press contributed to this report.