U.S. military aircraft launched an airstrike Friday morning in northern Iraq in response to attacks by Islamic militants on Kurdish forces.

Pentagon spokesman Rear Adm. John Kirby confirmed the bombing in a tweet Friday morning.

"US military aircraft conduct strike on ISIL artillery. Artillery was used against Kurdish forces defending Erbil, near US personnel," he wrote.

President Obama authorized the strikes Thursday to intervene in an intensifying humanitarian crisis after the Islamic State of Iraq and Syria swept into the region, forcing tens of thousands of members of a Kurdish religious minority into the mountains without food and water.

The ISIS attacks also were close enough to threaten U.S. military and other personnel in Irbil, a city of 1.5 million and the capital of Iraq's Kurdish region.

Irbil also is home to a U.S. Joint Special Operations Command, which has expanded in recent weeks as Obama has sent 750 military advisers to Iraq to help the Iraqi and Kurdish military fight ISIS.