Jim Michaels, Tom Vanden Brook and David Jackson

USA TODAY

WASHINGTON — U.S. warplanes made a second wave of airstrikes Friday in northern Iraq against the militants who have besieged a religious group and threatened the city of Irbil, a Pentagon official said.

Rear Adm. John Kirby, spokesman for Defense Secretary Chuck Hagel, said the second wave of strikes used a drone to attack a mortar position while four FA-18 fighter-attack planes hit a seven-vehicle convoy outside Irbil.

In a statement, Kirby said "shortly after 10 a.m. EDT, remotely piloted aircraft struck a terrorist mortar position." When the military returned to the site, they were attacked again "and successfully eliminated."

At 11:20 a.m. EDT, the second wave struck the convoy and the mortar position, Kirby said. "The aircraft executed two planned passes. On both runs, each aircraft dropped one laser-guided bomb, making a total of eight bombs dropped on target, neutralizing the mortar and convoy."

The drones involved in the strike were Predators, armed with Hellfire missiles, according to a Pentagon official who spoke about the operation on condition of anonymity because officials were not authorized to speak publicly on those details.

Assessment of the effects of the bombs was clear cut, the official said, because pilots can see the specific targets and the effect of 500-pound bombs and Hellfire missiles is "immediate."

The aircraft from the first strikes came from the USS George H.W. Bush, an aircraft carrier operating in the Persian Gulf, according to a second Defense official who spoke on condition of anonymity to discuss sensitive military details.

President Obama said Thursday night that airstrikes would be used if the militants threatened Irbil, home to a U.S. consulate and a joint U.S.-Iraqi operations center.

"As the president made clear, the United States military will continue to take direct action against ISIL (Islamic State of Iraq and the Levant) when they threaten our personnel and facilities," Kirby said in a statement Friday morning.

Strikes could continue through the weekend. Humanitarian-aid drops will continue as well.

White House spokesman Josh Earnest said Friday afternoon he had "no operational update" on airstrikes in Iraq, but said Obama's plan is "very limited in scope."

Obama's objectives are "protection of American personnel in Iraq," Earnest said, and answering the "urgent humanitarian situation at Sinjar Mountain," where members of an Iraqi religious minority, the Yazidis, are seeking refuge.

Hundreds of Yazidi women have been taken captive by ISIL members, the spokesman for Iraq's human rights ministry said Friday. Kamil Amin said the women are below the age of 35 and some are being held in schools in Iraq's second-largest city, Mosul. He said the ministry learned of the captives from their families.

Earnest said the U.S. mission against the Islamic State will not involve combat troops and will focus on helping improve Iraq forces so that they can take the lead in the fight against the militants.

The administration had developed the Iraq plan for some time, Earnest said, and Obama discussed Iraq and the Islamic State with House and Senate leaders in a mid-June meeting

Obama, congressional leaders and members of key committees also discussed Iraq at a meeting eight days ago, Earnest said. "We certainly welcome the partnership and support" of lawmakers, he said, adding that the White House contacted key leaders Thursday before the announcement of the strikes.

The administration has no plans to seek additional appropriations for the Iraq operation, Earnest said. The administration will maintain congressional consultations, and make notifications as required under the War Powers Resolution, he said.

Earnest said the plan will be evaluated regularly and assessed based on conditions on the ground.

"The president has not laid out a specific end date," Earnest said.

Obama has been briefed by national security aides throughout the day, Earnest said. In the morning, he spoke on the telephone with Jordan's King Abdullah, a longtime U.S. ally.

There are about 650 U.S. troops in Iraq — 470 of them to protect American personnel and property at the embassy and Baghdad International Airport. The remainder are there to assess the security situation in Iraq and assist Iraqi forces in dealing with the threat from Islamic extremists who have captured key cities.

The Pentagon also has dispatched Apache attack helicopters and surveillance aircraft to the airport. The drones and other manned spy planes have been flying dozens of missions daily.

Meanwhile, the Federal Aviation Administration announced Friday that it is banning U.S. airlines and commercial carriers from flying in Iraqi airspace.