( CNN ) -- The director of Iraq 's largest hydroelectric dam shot down reports Monday that it had been seized by the radical Islamic State , saying Kurdish forces fended off an assault . Fighters with the Islamic State , formerly the Islamic State in Iraq and Syria , or ISIS , were pushed back after gaining access to a housing compound for employees who work at the dam just north of Iraq 's second largest city , Mosul , Abdul Khaliq al-Dabbagh , the director of the Mosul Dam , said . Conflicting reports about who was in control of the dam on the Tigris River began Sunday amid news of fierce fighting between Islamic State fighters and Kurdish forces , known as Peshmerga . A Kurdish commander told CNN on Sunday that ISIS had taken control of it , though employees remained at the dam . But al-Dabbagh said the Peshmerga held their positions until reinforcements arrived early Monday morning . ISIS -- known for killing dozens of people at a time and carrying out public executions , crucifixions and other acts -- has taken over large swaths of northern and western Iraq as it seeks to create an Islamic state that stretches from Syria into Iraq . The United Nations in Iraq warned that 200,000 civilians were trapped in dire circumstances after the Islamic State and associated armed groups `` seized control of nearly all of Sinjar and Tal Afar districts '' in the northern Ninevah province , including several small oil fields that border Iraq 's Kurdish region . Most of the people who fled districts are minority Kurdish Yezidis , an ancient religious sect with ties to Islam , Christianity and Judaism . A large number have taken refuge in the Jabal Sinjar mountains , the United Nations said . Kurdish fighters battled ISIS in an attempt top retake Sinjar -- a small town inhabited by the Yezidi sect -- on Monday and have been engaged in house-to-house battles in some of the fiercest fighting since the fall of Mosul to the Islamic militant group in June , a Kurdish commander said . Both sides are using heavy weaponry , the source said . Fighting has also been reported in the border town of Rabia , with Syria-based Kurds joining the battle against Islamic State militants . Meanwhile , the head of the Kurdistan Regional Government , Massoud Barzani , told a group of Yezidi sect leaders that his government would liberate Sinjar , according to a report on the government 's website . Barzani said the Kurds had been fighting without any help from the Iraqi government or the international community . The State Department said Sunday that it was `` actively monitoring the situation '' in Sinjar and Tal Afar , and said that the United States is supporting both Iraqi security forces and Peshmerga forces in the fight against the Islamic State . `` The assault over the past 48 hours on territories along the border of the Iraqi Kurdistan Region and focusing on towns and villages populated by vulnerable minorities , demonstrates once again that this terrorist organization is a dire threat to all Iraqis , the entire region and the international community , '' State Department spokeswoman Jen Psaki said in a statement . Islamic State takes control of Iraq 's largest dam . U.S. agrees to send 5,000 more Hellfire missiles to Iraq .
NEW : Dam is in the hands of Kurdish forces , not the Islamic State , an official says . Comment: The Kurds are fighting ISIS and other groups that want to take over their region ( including al - Qaeda ). Kurdish fighters are engaged in house-to-house battle with Islamic State , source says . Sinjar fell to ISIS fighters over weekend , police say .