U.S. jet fighters carried out two airstrikes on Islamist militants outside the Kurdish regional capital of Irbil, hours after President Obama authorized attacks against the Sunni extremists advancing on the northern Iraq city.

The F-18 combat aircraft targeted artillery being used by militants of the Islamic State extremist group against Kurdish forces defending Irbil, the Pentagon said. It said the artillery was fired at Kurdish forces “near U.S. personnel.”

The planes dropped 500-pound laser-guided bombs at about 6:45 a.m. EDT, said Rear Adm. John F. Kirby, the Pentagon press secretary.

Obama authorized the strikes following the launch of a powerful offensive by Islamic State militants in northern Iraq. He also sent U.S. C-130 and C-17 transport aircraft to drop food and water to besieged Iraqi civilians in the region.

FA18 with laser guided bombs

(The fighters pictured are from VA-213 aboard the USS George H. W. Bush now deployed in the Persian Gulf.)