Kurdish Iraqi fighters took back much of a strategic dam in northern Iraq as the United States stepped up its bombardment of Islamic militant positions in the region, Kurdish officials said Sunday.
In comments to news agencies and on Iraqi television, the officials reported the gains at the Mosul dam, a massive structure on the Tigris River that is a key source of power and water for northern Iraq. Regaining control of the dam would be a major victory for Kurdish authorities, who were embarrassed in early August when Islamic State militants overran the dam and other areas nominally under Kurdish control, forcing a hasty withdrawal of peshmerga forces, as the Kurdish fighters are known.
The expanding presence of U.S. air power has clearly buoyed the spirits of the Kurdish fighters, who came under considerable criticism at home for their retreat in the face of the advance by the Islamic State, an Al Qaeda breakaway group.
Kurds on Sunday also took back several towns and villages from the militants, including Tel Skuf, according to news reports in Iraq.
In announcing the U.S. strikes, the Pentagon broadened the justification for them, saying for the first time that the United States was acting to support Iraqi and Kurdish troops. President Obama has said repeatedly that military action would be limited to protecting U.S. personnel in Iraq and giving humanitarian aid.
Kurdish authorities have voiced the hope that attacking in coordination with U.S. aerial forces would enable the peshmerga to win back much of the territory lost to the militants in early August. That would include the Sinjar area, where more than 200,000 members of the Yazidi sect fled in the wake of the militant onslaught.
But military commanders acknowledge that advancing into the militant-controlled city of Mosul, Iraq's second-largest urban area, will be a much larger challenge.
The Islamic State forces enjoy considerable support in Mosul, where many of the largely Sunni Muslim residents regarded the Shiite Muslim-dominated Iraqi army as an occupation force. Iraqi government troops pulled out of Mosul in June as militants overran the city with the help of local allies, including former stalwarts of the Baath Party of deposed dictator Saddam Hussein.
In Washington, the Pentagon said U.S. warplanes had stepped up attacks near the dam, conducting 14 strikes Sunday, the second day of the joint operation with Iraqi and Kurdish troops.
That was the greatest number of airstrikes carried out by the U.S. in a single day since the attacks began two weeks ago. For the first time, bombers were used along with fighters and drones. U.S. Central Command issued a statement saying the strikes had destroyed three armed vehicles, a vehicle-mounted antiaircraft artillery gun and a checkpoint.
"U.S. Central Command conducted these strikes under authority to support humanitarian efforts in Iraq, as well as to protect critical infrastructure, U.S. personnel and facilities, and support Iraqi security forces and Kurdish defense forces, who are working together to combat" extremist members of the Islamic State, the Pentagon statement said.
There were nine airstrikes around the dam and near the city of Irbil on Saturday.
The Rudaw Kurdish news site quoted a peshmerga commander as saying the Kurds had launched a "wide-ranging" assault in coordination with U.S. airstrikes. But the commander and Western officials monitoring the fighting said that progress was being slowed by explosives planted in the ground by fighters of the Islamic State.
The U.S. airstrikes have intensified since the resignation last week of Iraqi Prime Minister Nouri Maliki, whom the White House had pressed for months to step down.
The stepped-up military effort had been promised by the White House if Maliki left office.
Kurdish fighters, who retreated this month in the face of the extremist advance, have said they are outgunned by the Islamic State fighters. Kurdish authorities have requested additional arms, including heavy weapons, from the United States and Europe.
The United Nations has declared a Level 3 humanitarian emergency in Iraq, the most severe grade of humanitarian crisis.