US Aircraft Strike Islamic Militant Artillery In Iraq

The U.S. military backed up the Obama administration's vow to keep ISIS militants in Iraq out of a key northern city with at least one 500-pound laser-guided bomb dropped from American F/A-18 fighter jets on Friday. Sources confirmed to CBS News that the jets targeted an ISIS artillery piece that was shelling Kurdish forces near Erbil.

Sunni Islamic militants have stepped up efforts to expand their territory in northern Iraq, and their successes this week against what was thought to be the superior fighting force in the oil-rich, semi-autonomous Kurdish region prompted President Obama to threaten airstrikes.

"We will make sure that ISIL cannot approach Erbil," senior Obama administration officials told CBS News late Thursday, after Mr. Obama himself told the nation he had authorized airstrikes against the militant group.

CBS News senior defense correspondent David Martin said the Pentagon would authorize strikes if the militants from the Islamic State of Iraq and Syria (ISIS, also known as ISIL) didn't retreat from both the Sinjar mountains, where thousands of minority Yezidis have fled to avoid their advance, and from the area around Erbil, the capital of Iraq's Kurdish region.

With the militants showing no apparent signs of retreat and clashes with the Kurdish fighters continuing, the first strike came early Friday.

On Thursday, two U.S. military transport planes dropped tons of emergency food and water supplies onto the mountains for the displaced Iraqis.

About 150 U.S. military advisors and an unknown number of diplomats have relocated to Erbil in recent weeks as it was, until this week, considered relatively safe from ISIS attack.