BAGHDAD (Reuters) - When the Islamic State made another dramatic push through northern Iraq, many Iraqis fled their towns and villages before the Sunni militants notorious for beheadings arrived. 
 
 But the Yazidis of the town of Sinjar were especially terrified. The Islamic State, whose methods seem excessive even to al Qaeda, regards the minority ethnic group as "devil worshippers", making them prime candidates for the sword. 
 
 Tens of thousands fled the weekend assault on Sinjar and are now surrounded, according to witnesses and the United Nations, after the Sunni militants inflicted a humiliating defeat on Kurdish forces who had held towns in the area for years. 
 
 The Islamic State captured three towns and a fifth oil field and reached Iraq's biggest dam, consolidating gains made after a lightning sweep through the north in June which poses the biggest threat to Iraq since the fall of Saddam Hussein. 
 
 Residents said about 50 people were killed after the Sunni militants, who have declared parts of Iraq and Syria they control a caliphate, arrived in Sinjar late on Saturday. While 20 were killed trying to defend that town, it's not clear how the others died. 
 
 Many panicked Yazidis scrambled to find water and food for their children before climbing into their vehicles and rushing to surrounding mountains. 
 
 Some did not manage to escape. 
 
 "The innocent people of Sinjar were slaughtered. Men were killed and women have been taken as slaves by Islamic State fighters," said Vian Dakheel, a member of parliament from the Yazidi community, bursting into tears. 
 
 The Yazidis, followers of an ancient religion derived from Zoroastrianism, are spread over northern Iraq and are part of the country's Kurdish minority. 
 
 Many of their villages were destroyed when Saddam Hussein's troops tried to crush the Kurds. Some were taken away by the executed former dictator's intelligence agents. 
 
 Now they are on the defensive again years after the fall of Saddam raised hopes of a brighter future for all. 
 
 WHITE FLAGS 
 
 Some of the most vulnerable could not withstand the weekend offensive. Almost 70 children between the ages of one month and four died of thirst or hunger, said Dakheel. 
 
 The U.N. children's agency said families who fled the area are in immediate need of urgent assistance, including up to 25,000 children stranded in mountains. 
 
 "The reported deaths of 40 children from minority groups who were displaced from Sinjar city and district by armed violence are of extreme concern," UNICEF said in a statement. 
 
 "According to official reports received by UNICEF, these children from the Yazidi minority died as a direct consequence of violence, displacement and dehydration over the past two days." 
 
 Sinjar district's estimated population of 308,000 includes about 150,000 children, said UNICEF. 
 
 When the Islamic State swept into northern Iraq, the U.S.-trained army virtually crumbled. Thousands of soldiers fled. 
 
 Hoping to fill a security vacuum, Kurdish fighters known as peshmerga who often boast of their bravery in battles with Saddam Hussein's troops, stepped in, as did Shi'ite militias. 
 
 But the Islamic State routed the Kurds in the weekend surge, using artillery, mortars and machineguns seized from Iraqi soldiers compared to the Kurds' mostly AK-47 assault rifles. 
 
 "We are feeling so frustrated to see the peshmerga fleeing the town and leaving us alone face to face with Islamic State fighters," said farmer Haji Beso, 47, a resident of Sinjar who also operates a small pickup truck that transports goods. 
 
 "It was their duty to protect innocent people and die if they had to but they chose to flee without shooting a bullet." 
 
 Sinjar, the ancestral home to the Yazidi religious sect, felt helpless. Then the exodus began. 
 
 "After the peshmerga let us down and fled without fighting we couldn’t stay because we know that we would need a miracle to avoid the Islamic State's brutality," said Alyas Khudhir, a 33-year-old government employee with three children. 
 
 "I’m sleeping with my kids on rocks and food is scarce. I have collected some tree leafs to feed my kids if food runs out. We are slowly dying and nobody cares about us." 
 
 The refugees spoke to Reuters in telephone interviews. 
 
 While the Islamist State sets its sights on new territory, there is no sign Iraq's bickering politicians will be able to form a power-sharing government soon to counter the insurgency. 
 
 Prime Minister Nuri al-Maliki is defying calls by Sunnis, Kurds, some fellow Shi'ites and power broker Iran to step aside and make room for a less polarizing figure who could ease sectarian tensions causing the worst bloodshed since the height of a civil war in 2006-2007. 
 
 Maliki has ordered his air force to help the Kurds, who have vowed to launch a counter-offensive against the Islamic State. But there is little sign of relief on the ground. 
 
 Kareem Sido, 60, who grows tomatoes and cucumbers on his farm, decided to return to Sinjar when conditions on the mountain became too desperate. 
 
 Like many he was scared that snakes and scorpions could hurt his loved ones. After watching two babies die from the heat, he decided to return home. 
 
 On arrival, he was stopped at an Islamic State checkpoint. A fighter asked him why he had left and said there was no reason to fear the Islamic State, as long as he played by its rules. 
 
 "All you have to do is put a white flag on the roof of your house and declare you will obey us," Sido quoted the militant as saying. 
 
 When he climbed up to his roof he looked across Sinjar and saw a sea of white flags. 
 
 (Writing by Michael Georgy; Editing by Paul Taylor) ||||| Yazidi women who fled the violence in the northern Iraqi town of Sinjar sit Tuesday at a school where they are taking shelter, in the city of Dohuk in Iraq's semi-autonomous Kurdistan region. (Safin Hamed/AFP/Getty Images) 
 
 Stranded on a barren mountaintop, thousands of minority Iraqis are faced with a bleak choice: descend and risk slaughter at the hands of the encircled Sunni extremists or sit tight and risk dying of thirst. 
 
 Humanitarian agencies said Tuesday that between 10,000 and 40,000 civilians remain trapped on Mount Sinjar since being driven out of surrounding villages and the town of Sinjar two days earlier. But the mountain that had looked like a refuge is becoming a graveyard for their children. 
 
 Unable to dig deep into the rocky mountainside, displaced families said they have buried young and elderly victims of the harsh conditions in shallow graves, their bodies covered with stones. Iraqi government planes attempted to airdrop bottled water to the mountain on Monday night but reached few of those marooned. 
 
 “There are children dying on the mountain, on the roads,” said Marzio Babille, the Iraq representative for the United Nations Children’s Fund (UNICEF). “There is no water, there is no vegetation, they are completely cut off and surrounded by Islamic State. It’s a disaster, a total disaster.” 
 
 Most of those who fled Sinjar are from the minority Yazidi sect, which melds parts of ancient Zoroastrianism with Christianity and Islam. They are considered by the al-Qaeda-inspired Islamic State to be devil worshippers and apostates. 
 
 Iraqi politician Vian Dakhil makes a raw, emotional plea for the protection of the Yazidi people before Iraqi parliament. (YouTube/Al Sumaria TV) 
 
 The dramatic advance of the extremist Sunni fighters has torn the ethnic and religious fabric of the country, with Christians and Shiites also uprooted from cities and towns. 
 
 The Islamic State’s takeover of Sinjar, the first major setback for Kurdish forces protecting the country’s north, sent about 200,000 people fleeing, according to the United Nations. Some 147,000 have arrived in the semi-autonomous Kurdish region, flooding refugee camps. 
 
 Most of those stranded on Mount Sinjar had run out of battery life on their cellphones by Tuesday, but the few that still could communicate gave grim updates. 
 
 On Tuesday, 10 children and one elderly woman died, while on Monday, seven children had perished, said 23-year-old Shihab Balki, who was trapped with his mother, sister and four brothers. “I saw their bodies with my own eyes.” 
 
 He later texted the news of another casualty: a young man who had died of thirst, leaving his wife and five children behind. UNICEF said that 40 children had died after being displaced from their homes in the area in the 48 hours ending Monday night, including an unknown number on the mountain. The agency did not have figures for Tuesday. 
 
 In Baghdad, parliamentarians complained bitterly about the plight of the displaced, their discussions temporarily overshadowing wrangling over the nomination of a prime minister. 
 
 “Children have died because of dehydration and lack of food,” Vian Dakheel, a Yazidi parliamentarian from Sinjar, said through tears. “My people are being slaughtered,” she continued, referring to reports of mass killings of those who had stayed behind. 
 
 The ancient and secretive Yazidi sect, whose members number no more than 600,000 across Iraq, has suffered persecution for centuries. 
 
 Islamic State posted the first pictures of its capture of Sinjar on social networking sites on Tuesday. One showed six men lying face-down in a field, a pistol pointed at the backs of their heads. “Kill them wherever you find them,” read the caption. 
 
 Salem al-Sinjari, a 45-year-old teacher, said he’d seen around 25 bodies piled in the streets as he fled Sunday, leaving early enough to catch a ride to the Kurdish region. His mother, five brothers and two sisters wound up besieged on the mountain. He said he last spoke to them Monday before their last cellphone battery died. 
 
 Iraqi Kurdish security forces known as pesh merga are attempting to secure a road from the mountain to the nearby city of Rabia, but the process involves clearing villages where locals are sympathetic to the militants, said Majid Shingali, another local parliamentarian, who left Sinjar on Saturday. 
 
 Kurdish factions in neighboring Syria say they are entering Iraq to assist this country’s Kurds as they face Islamic State along a 650-mile front. 
 
 The Kurdistan Workers’ Party (PKK), designated a terrorist organization by the United States for its armed struggle against the Turkish state, also called for all Kurdish factions to unite against the Sunni extremists. 
 
 Babille, UNICEF’s Iraq representative, said that U.N. agencies have offered the Iraqi government technical assistance with airdrops but have yet to be asked for help. At least 15 to 20 flights would be needed just to provide those stranded with enough water and supplies to survive for a week, he said. 
 
 “We need to get them out,” he said. “If we don’t, it would be catastrophic.” 
 
 Mustafa Salim contributed to this report.
– The Islamic State regards Iraq's Yazidi minority as devil worshippers, so when militants captured the village of Sinjar this weekend, 60-year-old Yazidi farmer Kareem Sido fled to the mountains with thousands of others. What he found there were people dying of thirst in conditions so dire that he risked the trip home, Reuters reports. Up to 40,000 refugees remain on Mount Sinjar, however, surrounded by the extremists who attacked their village and who have a penchant for beheading dissenters. There is little food or water, and though the UN has offered to drop supplies, it hasn't been asked to do so by the Iraqi government. One witness tells the Washington Post that 10 children and one elderly woman died yesterday and seven children Monday; UNICEF believes 40 children have died since fleeing their village Monday night. "We need to get them out. If we don’t, it would be catastrophic," a UNICEF rep tells the Post. Going home would also spell death: "We would need a miracle to avoid the Islamic State's brutality," says one resident. There are about 308,000 Yazidi in Sinjar’s district; a minority sect of the Kurds, their religion is a combo of ancient Zoroastrianism, Christianity, and Islam. When the Islamic State came to Sinjar on Saturday, 20 Yazidi were killed in a failed defense and 30 more died of unknown causes. Many more fled—the US-trained army fell apart and the Kurdish pershmerga, mobilized to take their place, ran away "without shooting a bullet," one Sinjar resident tells Reuters. The Christian Science Monitor has this primer on the Yazidi people.