U.S. Planes Start Airstrikes on Iraq Militants

Two Jet Fighters Drop 500-Pound, Laser-Guided Bombs

This image from Associated Press video shows smoke rising from airstrikes targeting Islamic State militants outside the city of Erbil in northern Iraq on Friday. 

WASHINGTON—U.S. jet fighters hit artillery being used by the militant group called the Islamic State in northern Iraq on Friday, the first of what is expected to be a series of American strikes meant to halt the Sunni extremist advance on the Kurdish capital of Erbil, the Pentagon said.

The U.S. F/A-18 jet fighters dropped 500 pound laser-guided bombs on mobile-artillery positions outside Erbil, said Pentagon press secretary, Rear. Adm. John Kirby.

Defense officials said one artillery piece, towed by a truck, was destroyed in the strike. But officials wouldn't predict Friday if the limited first strike presaged a broader, lengthier campaign.

"The enemy gets a vote," said a senior defense official. "If they stop, we stop. If they attack we bring down the hammer."

Officials said it was too soon to tell if the current campaign would last weeks or days, but said they expect more strikes by U.S. fighter jets, as early as this weekend.