Militant hoisting the Islamic State flag, replacing the Kurdish flag tweeted by an account believed to be associated with the Islamic State @nynwa_news. Thousands of Yazidis stranded in the mountains of northern Iraq have been rescued, according to UN officials. Since August 3, tens of thousands of Yazidi men, women and children have been trapped there in scorching temperatures. At least 40 children died of thirst and another 25,000 are threatened with starvation. Yazidis are an Iraqi ethno-religious minority, who fled their homes in the ancient town Sinjar close to Iraq's autonomous region of Kurdistan and the Iraq -Syria border, after militants from the Islamic State (IS also known as ISIS) defeated Kurdish forces there on Sunday. Yazidis, like other minorities in Iraq, are the target of abductions and executions by Islamic State militants. Ethnically Kurdish, the Yazidi faith has some aspects of ancient Zoroastrianism. Many Iraqis refer to Yazidis as “devil-worshipers,” because their faith has a narrative of a fallen angel, similar to Satan in Abrahamic religions. As the extremist Sunni militant group Islamic State has been taking control of towns in western, and now northern Iraq, capturing one-fourth of Iraq's territory the last few months, the country's majority Shi'ites and minority Christians and Yazidis have been forced to flee their homes or face execution. Islamic State's war on “infidels” Not all Yazidi men and women made it out in time from Sinjar. Some Kurdish new sites put the number of killed between 100 and 2,000. Kurdish site Rudaw interviewed Yazidi refugees who put the number of killed at 300. They also said 500 women and girls were transported to Mosul to be “sold”. This isn't the first attempt by the Islamic State at ethnically cleansing an area of people viewed as ‘unworthy’ or as ‘infidels’. IS militants did the same with Assyrian Christians in Iraq's second largest city Mosul, which they captured on June 10, and Turkmen Shias in Guba and Shireekhan, which they've been in control of since June 23. Some Assyrian Christians and Turkmen Shia had actually fled and were seeking refuge among the Yazidis of Sinjar. The pattern seems to be the same: the Islamic State orders the civilian population to either evacuate their area, convert to Islam or face extermination. Bombing of holy sites important to Shias, Sunnis, Christians, Jews and/or Yazidis, is also very common. Ayub Nuri writes on the Kurdish website Rudaw: Shingal [Sinjar] is occupied by a group that has no business being there. Do they hope to convert the local population to Islam? Do they hope to stay forever? It is impossible. The Yezidis have held on to their beliefs for 4,000 years. They have resisted, defied and survived the first Islamic conquest and hundreds of years of subsequent persecution and degradation at the hands of their neighbors. They will not give up now. Like the people of Leningrad during World War II, they would rather resist not five days but five years than descend the mountain and submit to the will of a radical group that commits a massacre wherever it goes. […] The people of Leningrad withstood a siege by Hitler’s forces that lasted almost three years until they saw their enemy defeated. The Yezidi Kurds will also see the backs of their enemies and will sooner or later return to rebuild their homes and shrines. But why to sit and watch them die? Young men from every corner of Kurdistan have taken up arms and are now fighting for Shingal. The whole world should do the same. The Islamic State (IS), also known as the Islamic State of Iraq and the Levant (ISIS) used to be al Qaeda in Iraq. But the IS and al-Qaeda officially divorced in February 2014, after IS reportedly defied repeated orders to kill fewer civilians in Syria. Since June 10, IS has taken control of five oil fields in Iraq. Some experts believe IS may overtake al-Qaeda as the most influential extremist group in the world. The group now controls a third of Syria and a quarter of Iraq, an area equivalent to the size of Great Britain. Kurdish forces take on the Islamic State The takeover of Sinjar was the first major setback for Kurdish forces, who have been defending northern Iraq from advances from the Islamic State. At the time of writing, Kurdish forces are planning a counter-attack. Iraq's Prime Minister Nouri al-Maliki has also ordered his air force to back Kurdish forces. Up until now Maliki has been at odds with Kurdish forces from Iraq's semi-autonomous Kurdistan, in the fight against the Islamic State. After the Islamic State seized Mosul, Kurdish forces took control of neighboring Kirkuk, a strategic oil town, which did not go down well with Maliki.