Kurdish forces took over parts of Iraq's largest dam yesterday less than two weeks after it was captured by the Islamic State extremist group, Kurdish security officials said.
US and Iraqi planes aided their advance by bombing militant targets near the facility.
The US began targeting Islamic State fighters with airstrikes a little more than a week ago, allowing Kurdish forces to fend off an advance on their regional capital Arbil and to help tens of thousands of members of religious minorities escape the extremists' onslaught.
Recapturing Mosul dam would be a significant victory against the Islamic State group, which has seized vast swaths of northern and western Iraq and northeastern Syria. The dam on the Tigris supplies electricity and water for irrigation to a large part of the country.
The Kurdish forces, known as peshmerga, launched the operation early yesterday to retake the dam, said General Tawfik Desty, a Kurdish commander. He said his forces now controlled the eastern part of the dam and that fighting was still under way.
Another commander said Kurdish forces were hindered by roadside bombs planted by retreating Islamic State fighters. He added that peshmerga forces had taken the nearby town of Tel Kasouf yesterday morning.
"They are advancing slowly. The obstacles are the roadside bombs. It's a Daash tactic," he said, referring to Islamic State by an Arabic acronym.
"They have reached inside the dam. There is no fighting, just the [roadside] bombs, and the abandoned buildings are all rigged with explosives," he said. "We will continue to advance and advance until we are given further instructions."
He said the peshmerga were now waiting for 15 Iraqi military Humvees with mechanised bomb-disposal units. He said some of the explosives had been placed in abandoned buildings by Iraqi troops in an earlier bid to stall the militants' advance.
On Saturday, the US said nine airstrikes had been launched near the dam, destroying four armoured personnel carriers, seven armed vehicles, two Humvees and another armoured vehicle.