— American warplanes and drones struck Islamist militants near this northern Iraqi city Friday, putting the U.S. military back in action in the skies over Iraq less than three years after the troops withdrew and President Obama declared the war over.

The strikes were limited in scope but helped temper days of building panic across the north of the country as militants with the extremist Islamic State sliced through a string of towns and villages scattered on the outskirts of the Kurdish region and sent tens of thousands of civilians fleeing for their lives.

The airstrikes also presented the first significant challenge yet to months of unchecked expansion by the al-Qaeda offshoot, which has swept through much of Iraq and neighboring Syria over the past year, annihilating its opponents, capturing valuable resources and declaring the creation of an Islamic caliphate in a nation-size chunk of territory.

In Washington, the Pentagon announced three separate strikes by multiple aircraft against militant positions it said were firing on Kurdish forces protecting Irbil, saying that they had “successfully eliminated” artillery, a mortar position and a convoy of extremist fighters. Kurdish media and officials, who said the attacks had had a “devastating” impact on militant positions, claimed other, unconfirmed attacks that were farther afield.

U.S. officials also stressed that the American intervention was narrowly aimed at the protection of American diplomats and officials living in Irbil, where the large U.S. consulate has swelled with evacuees from the embassy in Baghdad and where the U.S. military runs a joint operations center alongside Kurdish forces.

“There are American military and diplomatic personnel in Irbil,” White House press secretary Josh Earnest said at a news briefing in Washington. “The protection of American personnel in Iraq is a top priority and one that merits the use of military force.”

He emphasized that the authorization for airstrikes “is very limited in scope” but did not rule out that there may be additional strikes to protect some of the tens of thousands of members of the minority Yazidi faith trapped by Islamic State fighters on a mountaintop.

The government of current Prime Minister Nouri al-Maliki requested the U.S. intervention, Earnest said. But he and other U.S. officials made clear that more comprehensive U.S. engagement in the battle against the militants will not happen unless feuding politicians in Baghdad establish a more inclusive government capable of resolving Sunni grievances that facilitated the Islamic State’s rapid expansion.

The Iraqi parliament is scheduled to choose a new prime minister, perhaps as early as Sunday, according to U.S. officials who have made clear their preference that Maliki stand down.

U.S. aircraft go into action

The first of the airstrikes came in the early afternoon — at dawn Washington time — and were carried out by two F/A-18 combat jets flying from the aircraft carrier USS George H.W. Bush in the Persian Gulf. The aircraft dropped 500-pound laser-guided bombs on a mobile artillery piece that had been used to shell Kurdish positions, the Pentagon said. The strike occurred in Makhmour, a town southwest of Irbil, according to Mahmood Haji, an official at the Kurdish Interior Ministry.

Two more announced strikes came in late afternoon, Iraq time. An MQ-1 Predator drone armed with Hellfire missiles struck an Islamic State mortar position. When fighters returned to the site moments later, “the terrorists were attacked again and successfully eliminated,” according to Pentagon spokesman Rear Adm. John F. Kirby.

Less than an hour later, four aircraft dropped eight laser-guided bombs on a seven-vehicle convoy and a mortar position nearby, the Pentagon said. Those strikes took place near the Khazer checkpoint on the road between Mosul and Irbil, according to Haji, the Kurdish official.

Map: U.S. airstrikes in Northern Iraq

As news of the strikes spread, jihadist fighters and supporters took to Twitter to express glee that the United States had become embroiled in their battle, threatening to shoot down planes, exact revenge and conquer other American allies elsewhere in the region.

“This crisis will become a gift and you shall remember this: Our State will enter Irbil and America will fall, and then the Gulf will be ours,” one purported jihadist tweeted.

“Your announcements do not scare us; the biggest enemy of the State is the Americans,” said another.

President Obama authorized the strikes in response to a powerful Islamic State offensive launched a week ago across northern Iraq in which towns and villages occupied mainly by members of Iraq’s ancient Christian minority, as well as the Yazidis, have been overrun.

At the same time, he dispatched U.S. military aircraft to drop food and water to the besieged Yazidis, who fled the town of Sinjar to a nearby mountain to escape the advancing militants. Obama said airstrikes might also be used to break the militant siege of the mountaintop, if Kurdish forces are unable to do so.

The pentagon announced late Friday that it had made a second airdrop of food and water to the stranded Yazidis.

Intervention welcomed

After weeks of appealing to the United States for arms and ammunition to help in the fight against militants, Kurdish officials expressed gratitude for the intervention.

“We never lost hope that our friends would come when the circumstances were there,” former Iraqi foreign minister Hoshyar Zebari told reporters in Irbil.

He said the strikes had made a significant impact on the ground and would enable Kurdish forces to regain territory they have lost to the extremists in the past week.

“Our intelligence . . . is that it has been a devastating blow” to the militants, Zebari said. “Commanders have seen dramatic changes on the front lines. . . . We have already seen some withdrawals.”

Whether strikes limited to the northeastern edge of the vast territory controlled by the Islamic State will degrade its control elsewhere is in question, however.

U.S. officials have encouraged cooperation between Iraqi government and Kurdish forces. On Friday, Iraqi forces “delivered a planeload of ammunition to Irbil to resupply Kurdish stockpiles — which is unprecedented,” one official said.

“We have now received a request from Kurdish forces for small arms and ammunition, including mortars and AK-47 assault rifles. The U.S. government is coordinating with the government of Iraq to help fill these requests as quickly as possible,” the official said.

Response to the airstrikes was limited from the U.S. Congress, which is in the midst of a late-summer recess. While most members who offered an opinion supported Obama’s decision, some Republicans criticized him as waiting too long while Islamic State forces spread across Iraq over the past two months.

Others warned Obama against expanding the effort without seeking congressional approval.

“If further sustained military action is necessary, it is incumbent on Congress to review all the facts, debate the issue and vote to authorize any additional sustained military action,” Rep. Robert C. “Bobby” Scott (D-Va.) said in a statement.

Three main factors motivated Obama’s decision to authorize the airstrikes and humanitarian airdrops, Earnest said: the “deeply disturbing” situation at Mount Sinjar; reports that Islamic State insurgents were advancing toward Irbil; and the progress that Iraqi politicians have made in forming a new government after months of stalemate since parliamentary elections were held.

He said he was “not in a position to offer a specific date” on when the campaign would end, but he reiterated Obama’s pledge that “the United States will not be dragged back into a prolonged military conflict in Iraq” and that the intervention would not include ground troops.

DeYoung reported from Washington and Morris from Baghdad.