Backed by U.S. airstrikes that began in Iraq late Saturday, Iraqi special forces, allied tribesmen and local police launched a ground offensive Sunday to drive Islamic State militants out of the Haditha area.

The extremists have been attempting to break into the city and take control of its hydroelectric dam since late June, with Iraqi security forces and tribesmen holding back the near-daily assaults, said Khalid Salman Rasif, head of Haditha’s local council.

“The Iraqi army and the tribes have been surrounding Haditha to protect it, but today the special forces joined and the operation started to liberate the area,” he said. “We are on the attack.”

Brig. Gen. Abdulwahab al-Saidi, an Anbar-based special forces commander, said the ground offensive was launched about 6 a.m. Iraqi special forces are calling in targets for U.S. airstrikes, he said.

The target of the operation is outlying villages and towns controlled by the Islamic State including Barwana, just outside Haditha on the eastern banks of the Euphrates River. Saidi, who spoke from the battlefield in Barwana, said he expected the town to be fully secured by Sunday evening.

Islamic State fighters had been threatening to seize control of the Haditha Dam, seen in this 2004 file photo, which generates electricity for much of Iraq. (Doug Struck/The Washington Post)

“We’ve cut Daash’s heads,” one tribal fighter interviewed but not identified by Iraqi television channel Al Anbar said, thanking Iraqi special forces for providing them with weapons to join the fight. “We are the real tribal revolutionaries, the one who are defending our cities.”

Saturday’s late night airstrikes were carried out against targets near Haditha Dam, which stretches more than five miles across the ancient Euphrates River in western Iraq, about 150 miles northwest of Baghdad, according to a Pentagon statement.

The airstrikes were carried out against targets near Haditha Dam, which stretches more than five miles across the ancient Euphrates River in western Iraq, about 150 miles northwest of Baghdad, according to a Pentagon statement.

The attacks marked a sharp escalation of the U.S. military campaign that began Aug. 8, when President Obama ordered the Pentagon to intervene in Iraq to stem the rapid advance of Islamic State, a well-armed Sunni extremist group that has swept across the north and west of the country.

Officials from the U.S. Central Command, which oversees military operations in the Middle East, said a mix of fighter and bomber aircraft carried out four separate attacks Saturday near the dam. The strikes, they said, destroyed five Humvees that had been captured by Islamic State militants from Iraqi security forces, an armed vehicle and a checkpoint.

U.S. officials said all their aircraft exited the area safely. Central Command did not specify what types of aircraft were deployed or where they flew from. But the U.S. military has been spearheading its campaign in Iraq from three air bases in the Persian Gulf.

In remarks to reporters Sunday during a visit to Tbilisi, Georgia, Defense Secretary Chuck Hagel called the dam “a critically important facility” and said the strikes “are very much in line with what President Obama said were the guiding principles of military action in Iraq.”

Hagel said the operation was planned and coordinated with Iraqi government troops on the ground. The Iraqi government had been pressing the U.S. military to call in airstrikes around Haditha for the past few weeks.

For now, Obama has imposed tight limitations on the U.S. military operations, directing the Pentagon to take action only to prevent civilian massacres and other humanitarian disasters, or to protect U.S. personnel and diplomatic facilities in Iraq.

Those actions are intended to buy time until the White House and Pentagon can put together plans for a broader and more extensive military campaign against Islamic State. Obama has said that strategy would rely heavily on cooperation from the often-dysfunctional Iraqi government, Kurdish forces, NATO allies and other countries in the Middle East.

Before Saturday, the U.S. military had conducted 133 airstrikes against Islamic State forces, all in northern Iraq. The bulk were carried out to help Kurdish and Iraqi government troops re-take control of the Mosul Dam, the country’s biggest, which holds back the Tigris River but had been captured by Islamic State in early August.

Other strikes have been aimed at preventing Islamic State fighters from marching on Irbil, the Kurdish regional capital, and massacring refugees from Iraqi minority groups. U.S. military aircraft have also conducted a series of airdrops to deliver food, water and medical supplies to tens of thousands of refugees surrounded by Islamic State.

Saturday’s strikes by the U.S. military were the first in Iraq’s Sunni-dominated Anbar province, which has been under the control of Islamic State for nearly nine months. The escalation in airstrikes came as Hagel was visiting Tbilisi, Georgia, as part of an overseas trip designed largely to recruit allies and other countries to participate in the U.S.-led coalition against Islamic State.

U.S. commanders have long viewed Haditha Dam as critical ground. Strikes to save it from Islamic State fighters harken back to the early days of the U.S. invasion in the spring of 2003 when American special operations forces were sent into Iraq to seize the dam to prevent Saddam Hussein’s troops from destroying it and flooding Shiite cities to the south.

U.S. officials said Saturday’s airstrikes around Haditha were conducted under Obama’s previous authorization to prevent humanitarian disasters. Had the dam fallen into extremist hands, they said, Shiite areas to the south once again would be at risk of flooding and Iraq’s electricity supply would be endangered.

Like much of Anbar province, the area around the dam saw heavy fighting throughout the U.S. occupation that ended only when Sunni tribes in the area turned on al-Qaeda-affiliated fighters and formed their own U.S. supported tribal militias.

Senior U.S. officials have expressed hope that if Iraq’s new prime minister designate can form an inclusive government in Baghdad, it could provide some Sunni tribal leaders, chafing under harsh Islamic State rule, to rise up. Anbar province, which includes the Haditha area, is significant because since 2003 it has been the heartland of most of the major Sunni insurgent movements.

The town of Haditha is also known as the site of an alleged massacre in which 24 unarmed Iraqi men, women and children were killed by U.S. Marines. The region lies in the Euphrates River Valley, which during the Iraq war was a major supply line for insurgents moving people and explosives from Syria into Baghdad.

It is unlikely that airstrikes around the Haditha dam by themselves would do anything to shift the balance of power in the region.

Islamic State has quickly emerged as a powerful insurgency, drawing strength from thousands of foreign fighters who have joined its ranks in Syria and Iraq. The group has declared itself the ruler of a modern-day Islamic caliphate while embracing brutal tactics, including mass killings of Iraqi minority groups and the beheadings of two American journalists.

The movement has fought the army of Syrian President Bashar al-Assad to a standstill. This spring and summer it pushed across Iraq and closed within about 50 miles of Baghdad, overrunning Iraqi government troops and seizing their U.S.-made weapons.

Obama has vowed to “destroy” the group, but has also promised not to send U.S. ground troops back into combat in Iraq — less than three years after the end of the last U.S. war in the country.

Since June, however, he has authorized the deployment of 1,100 U.S. troops to Iraq, most of them to defend the U.S. embassy in Baghdad, the international airport in the capital, and the U.S. consulate in Irbil. Others have been assigned to coordinate and advise Kurdish and Iraqi security forces.

Whitlock reported from Tbilisi, Georgia. Jaffe reported from Irbil, Iraq.