Turkey should face an international court for complicity in acts of genocide against the Yazidis, while Syria and Iraq failed in their duty to prevent killings, according to an investigation endorsed by British human rights lawyer Helena Kennedy, The Guardian reported.

The report, written by a group of prominent human rights lawyers, attempts to underscore the imperative responsibility of states to prevent genocide on their soil, even if it is carried out by a third party, the Islamic State (IS).

Lawyers, United by the Yezidi Justice Committee (YJC), said that under international law, states have a responsibility to prevent the crime of genocide in accordance with the Genocide Convention. Sir Geoffrey Nice QC, chairman of the YJC, described the Yazidi genocide as "insanity".

Since 2013, it is acknowledged that there have been genocide attempts against the Yezidis, a religious minority, in Iraq and Syria. The report, prepared after a three-year investigation into the behavior of 13 countries, concluded that three of them had failed in their duty to prevent genocide.

In the case of Turkey, the committee went even further, accusing the leaders of complicity in the massacres, arguing that they had not established control over their borders to stop the free flow of IS fighters, including a significant number of Turkish citizens.

The committee said that since April 2014, Turkish officials have turned a blind eye to the sale, transfer and enslavement of Yazidi women and children and have helped train ISIS-linked fighters to fight the Kurds in Syria, thus strengthening the perpetrators of the genocide.

“Turkish officials knew and/or deliberately turned a blind eye to evidence that these individuals would use this training to carry out prohibited acts against the Yazidis,” the report says.

The report notes that similar allegations have been made against some Gulf states, including Qatar, but insufficient evidence has been provided.