“The militants want to spread horror among them to force them to convert to Islam or to do something else,” Mr Khalil said.
He added that those killed included men, women and the elderly. He said he believes some 1,400 other Yazidis are still held in the camp.
Iraqi Vice-President, Osama al-Nujaifi said in a statement on Facebook that the reported deaths were “horrific and barbaric”.
Tens of thousands of members of the religious minority group fled in August when militants from the Islamic State group captured the northern town of Sinjar, near the Syrian border.
But hundreds were taken captive, with some Yazidi women forced into slavery, according to international rights groups and Iraqi officials.
About 50,000 Yazidis – half of them children, according to UN figures – fled to the mountains outside Sinjar during the onslaught. Some still remain there.