With the support of US air strikes, the ground forces launched the operation to take Mosul dam on Sunday morning.
According to Kurdish sources, they were still trying to clear mines and booby traps from the area round the dam. The process could take several hours.
The strategically important facility -- Mosul dam -- was seized by IS militants Aug 7. It supplies water and electricity to northern Iraq and there had been fears the IS militants could use it to flood areas downstream.
Formerly called as ISIS, the Islamic State or, IS has seized a swathe of territory in recent months in Iraq and Syria. If the recapture of the dam is confirmed, it will be the biggest reverse for IS since it launched its offensive in Iraq in June.