US military aircraft have been dropping food and water to tens of thousands of people trapped on a mountaintop by Islamic State (IS) militants near the northern Iraqi town of Sinjar.
It has been reported that around 30,000 of 50,000 Yazidi Kurds, Christians and minority groups have received aid.
The Islamic State considers the Yazidis to be “devil worshippers”.
US President Barack Obama expressed his outrage at the situation: “We have begun a humanitarian effort to help those Iraqi civilians trapped on that mountain.”
“The terrorists that have taken over parts of Iraq have been especially brutal to religious minorities,rounding up families, executing men, enslaving women, and threatening the systematic destruction of an entire religious community, which would be genocide,” Obama said.
The United Nations said that some 200,000 people fleeing the advance of the Islamists had reached the town of Dohuk on Tigris River in Iraqi Kurdistan.
Tens of thousands of people have fled north to the Turkish border, according to Ankara.
Around 4,000 Christians have been seeking refuge in a church in Irbil, after travelling from nearby Ninewa Province.
Jose Hanna, a displaced Iraqi, asked: “Many of my family are still trapped there, why? Why can’t we reach a solution, all my relatives are there, waiting, what have we done to deserve this?”
As well as threatening Yazidis and Christians, Islamic State fighters have crushed Kurdish Peshmerga forces.
The Autonomous Kurdish region had been the only part of Iraq to survive the past decade of civil war without a serious security threat.