Baghdad, Iraq (CNN) -- U.S. warplanes on Saturday pounded a series of extremist militant targets in what officials say is part of an effort to retake a key piece of infrastructure in northern Iraq -- Mosul Dam.
The airstrikes against fighters of the so-called Islamic State come amid growing concern that the dam is not being properly maintained and could rupture, a U.S. official familiar with the details told CNN.
Engineering studies have shown that a failure of the dam would be catastrophic, resulting in flooding all the way to Baghdad, the official said on condition of anonymity.
Mosul Dam is Iraq's largest hydroelectric dam, and it sits on the Tigris Rivers about 50 kilometers (31 miles) north of the city of Mosul. ISIS fighters took control of the dam this month following fierce fighting.
The United States estimates there may be up to 400 ISIS fighters in and around the dam complex, said the U.S. official.
The U.S. military confirmed a mix of fighter jets and drones carried out nine airstrikes near Mosul and the Kurdish regional capital of Irbil. The strikes targeted armored vehicles being used by ISIS fighters, it said.
U.S. Central Command declined to provide further details, citing security of its personnel.
There were conflicting reports from Kurdish officials about whether its military force, known as the Peshmerga, had begun a ground operation to retake the dam.
Mosul Dam remains in hands of ISIS
A colonel with the Peshmerga told CNN the operation began early Saturday with Kurdish forces advancing toward the dam as the United States carried out airstrikes against "mobile ISIS positions."
The dam complex has not been hit, the colonel said on condition of anonymity. He is not authorized to speak to the media.
While Peshmerga spokesman Hilgurd Hikmat also confirmed the U.S. airstrikes, he said the Kurdish forces are not on the move and have not engaged in battle with ISIS fighters near the dam.
Mosul Dam is under ISIS control, but it is still up and running, the colonel said. Engineers and employees remain at work, he said.
U.S. intelligence agencies, according to the U.S. official, are also keeping an eye on the Haditha Dam on the Euphrates River in Iraq's western Anbar province, where Iraqi troops have been holding off an ISIS assault for weeks.
The dam is the second-largest in the country, and it provides water to western and southern Iraq. A failure of the Haditha Dam also would prove catastrophic.
Earlier this year, ISIS fighters opened the gates on the Falluja dam after seizing it in an effort to stop an Iraqi military advance. The water from the dam flooded a number of small villages.
U.S. President Barack Obama ordered targeted airstrikes to protect U.S. personnel and facilities in Iraq and prevent a potential genocide of ethnic and religious minority groups by ISIS, also known as the Islamic State in Iraq and Syria.
American airstrikes were carried out near the Yazidi village of Kojo amid reports that ISIS fighters had launched an attack, the U.S. military said.
Yazidi men killed, women abducted
ISIS swept into the village on Friday, killing at least 80 men and taking more than 100 women captive, officials told CNN. One Yazidi leader put the death toll much higher.
The report of the brutal attack on the village of Kojo came after Obama -- citing the success of targeted American airstrikes -- declared an end to an ISIS siege that had trapped tens of thousands of Yazidis in mountains.
A Yazidi leader, Mirza Dinnayi, told British broadcaster Channel Four News that more than 350 men were killed and 1,000 women and children kidnapped during the attack.
Fighters with ISIS attacked Kojo after surrounding it for days, a Kurdish regional government official and a Yazidi religious leader said.
The women abducted from the village were being taken to the ISIS-controlled northern cities of Mosul and Tal Afar, the official said.
CNN cannot independently confirm the killings and abductions, but the claims are similar to reports provided by survivors of ISIS attacks in Iraq.
The Yazidis, one of Iraq's smallest and oldest religious minorities, are among 400,000 people that the United Nations estimates have been driven from their homes since June, when ISIS swept across the border from Syria into Iraq.
Jomana Karadsheh reported from Baghdad, Barbara Starr from Washington and Chelsea J. Carter reported and wrote from Atlanta. CNN's Anna Coren, Mohammed Tawfeeq and Mariano Castillo contributed to this report.