Officials said Iraqi and U.S. troops have targeted Al Qaida strongholds in the Diyala province north of Baghdad. They said Operation Lightning Hammer was aimed at the Sunni and Al Qaida infrastructure in the fertile crescent of the Diyala River.

"Al Qaida cells were disrupted and forced into hiding in June and July," U.S. Army Maj. Gen. Benjamin Mixon, the commander of U.S. forces north of Baghdad, said. "Our main goal with Lightning Hammer is to eliminate the terrorist organizations and show them that they truly have no safe haven — especially in Diyala."

Officials said 16,000 Iraqi and U.S. troops were participating in Operation Lightning Hammer. They said the operation, launched on Aug. 13, sought to block the flow of insurgents and car bombs into Baghdad.

Operation Lightning Hammer began with a late-night air assault along the Diyala River. Officials said the air attacks targeted newly-established Sunni strongholds that had been transferred from the Diyala capital of Baquba.

"The Iraqi Army and coalition forces are committed to the people of Diyala, they are committed to fighting for the Iraqi people's security," Mixon said. "We will aggressively and persistently target Al Qaida, an organization that brings nothing but hatred, destruction, and disregard for the very foundation of the Iraqi peoples' principles and faith."

The latest mission was said to have marked a new stage of Operation Phantom Strike. Officials said Phantom Strike, launched in June 2007, was meant to target Al Qaida and Sunni cells north of Baghdad. They said more than 200 Al Qaida and Sunni insurgents were killed and more than 160 were arrested during the operation.

"My intent is to continue to pressure [Al Qaida] and other extremist elements throughout Iraq to reduce their capabilities," Lt. Gen. Ray Odierno, the No. 2 U.S. commander in Iraq, said.