The development marks the first major victory for Iraqi and Kurdish troops since US airstrikes began earlier this month and could significantly boost their morale as they try to free territory overrun by the Islamic State group in a blitz this summer.
The Mosul Dam spanning the Tigris River just north of Iraq's second-largest city of Mosul and its broader complex hold great strategic value as they supply electricity and water to a large part of the country.
Army spokesman Lt. Gen. Qassim al-Moussawi told The Associated Press that Kurdish peshmerga forces and Iraqi anti-terrorism troops "fully liberated" the dam today and "hoisted the Iraqi flag over it."
Al-Mousawi added that the troops were backed by a joint aerial support, but he didn't specify whether there were any US airstrikes in the area of the dam today.
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The US launched airstrikes against the Islamic State group in Iraq more than a week ago in a bid to halt its advance across the north.
But the Sunni militants remain in control of vast swaths of northern and western Iraq, including the city of Mosul, as well as much of northeastern Syria.
Some 1.5 million people have been displaced by fighting in Iraq since the Islamic State's rapid advance began in June.
The scale of the humanitarian crisis prompted the UN to declare its highest level of emergency lasts week.