London, Asharq Al-Awsat—The Islamic State of Iraq and Syria (ISIS) tortured and attempted to indoctrinate Kurdish children from the besieged Syrian town of Kobani, Human Rights Watch (HRW) said on Tuesday.

Four boys aged 14-16 told the rights watchdog that they were beaten with hoses and electric cables and were forced to watch videos of ISIS beheadings while being held captive by the extremist group for four months, along with 100 other children.

HRW spoke to the boys in Turkey after they were released by ISIS in late September. The reason for their release is unknown, although the boys said that they were told that they were free to go as their training was complete.

The children were held in a school building in Manbij, a town 34 miles (55 km) southwest of Kobani. Several of the child hostages managed to escape while others were reportedly released as part of prisoner exchanges.

According to the boys’ testimonies, children with family ties to the People’s Protection Units (YPG), the Kurdish group fighting ISIS in Kobani, received the harshest treatment.

“They [ISIS] told them to give them the addresses of their families, cousins, uncles, saying ‘When we go to Kobani we will get them and cut them up.’ They saw the YPG as kafir [unbelievers],” said one of the boys, aged 15.

All of the children described being forced to undergo intense religious instruction. One of the boys interviewed said that those who did not conform to the program were beaten. He explained how they were beaten on the soles of their feet and subjected to the dulab (tire) torture method. The dulab has long been used as a form of torture in Syria whereby the victim is forced into a vehicle tire which is often hoisted up and the individual is beaten on the feet.

The boys were among 250 children who were kidnapped in Aleppo governorate on their way back home from school on May 29, 2014. The girls in the group, numbering around 100, were released within hours, while 153 boys remained in captivity.

The battle for Kobani between ISIS and Kurdish fighters has been raging for more than a month and coalition air strikes have failed to push the Islamist group out of the town. The Kurds received reinforcements from Iraqi Kurdistan and the Free Syrian Army (FSA) last week in a renewed effort to reverse the advance of ISIS fighters.

The Iraqi-Kurdish Peshmerga and FSA targeted ISIS positions with cannon and mortar fire on Monday, according to Reuters news agency.

Another 93 Kurds held hostage by ISIS were released on Monday according to the UK-based Syrian Observatory for Human Rights.

The US military said on Monday that coalition forces had bombed ISIS positions in Syria 17 times and in Iraq 16 times since Friday, including near Kobani.

The organization also gained fresh international notoriety this week after a video emerged on social media networks purporting to show ISIS members discussing the purchase of Yazidi girls as slaves.

The group overran parts of northern Iraq home to the Yazidi religious minority earlier this year, reportedly massacring hundreds of men and taking hundreds more women and girls prisoner.

An article in a recent issue of what claims to be ISIS’s official magazine, Dabiq, said that female Yazidi captives had been distributed among its fighters as spoils of war.

“After capture, the Yazidi women and children were then divided according to the Shari’a among the fighters of [ISIS] who participated,” it said.