ASSOCIATED PRESS The covered body of Kamal Abdulsalam, mayor of Karmah and one of more than 20 people killed in a suicide attack, arrives at a hospital in Fallujah, west of Baghdad. A suicide bomber struck Thursday inside a municipal building in Karmah during a meeting of tribal sheiks opposed to al-Qaida, police said.

Al-Qaida claims role in attack in Iraq

» Fellow Kaneohe Marines react to the deaths

BAGHDAD » An al-Qaida front organization claimed responsibility yesterday for a suicide bombing that killed more than 20 people -- including three Kaneohe-based Marines -- as the U.S. military stepped up pressure on extremists in northern Iraq.

The Islamic State of Iraq posted the claim on a militant Web site, saying the bomber blew himself up among a gathering of the "heads of apostasy" -- a reference to U.S.-backed Sunni tribal leaders who were attending a meeting Thursday in Karmah, 20 miles west of Baghdad.

"They sold their souls to the American devil for a cheap price," the statement said. "Therefore, the soldiers of the Islamic State of Iraq have launched an open war against them."

The dead included several key tribal figures, U.S. and Iraqi officials said.

It could not be determined if the statement was actually issued by the Islamic State, which is an al-Qaida-controlled coalition of Sunni extremist groups.

However, U.S. officials suspected al-Qaida was behind the attack as part of a campaign of revenge against Sunni community leaders who turned against the terror movement and cooperated with U.S. and Iraqi authorities.

The Sunni revolt against al-Qaida, which gained steam two years ago, cost the terror movement much of its base in vast Anbar province, the heartland of Iraqi's Sunni Arab community and former center-stage of the Sunni insurgency against U.S.-led coalition forces.

The Karmah attack happened two days before U.S. officials planned to formally hand over security responsibility for Anbar to the Iraqis -- a sign of the security transformation in the largest of Iraq's 18 provinces. U.S. authorities postponed the ceremony Friday because of forecast sandstorms.

Elsewhere, the U.S. command said American and Iraqi soldiers stepped up pressure this weekend on al-Qaida and other Sunni militants across northern Iraq.