Baghdad ? A suicide bomber killed at least 55 people Thursday in a packed restaurant near the northern city of Kirkuk where Kurdish officials and Arab tribal leaders were trying to reconcile their differences over control of the oil-rich region.

The brazen attack — the deadliest in Iraq in six months — occurred at a time of rising tension between Kurds and Arabs over oil, political power and Kirkuk.

No group claimed responsibility for the attack at the upscale Abdullah restaurant, which was crowded with families celebrating the end of the four-day Islamic holiday of Eid al-Adha. The U.S. blamed the blast on al-Qaida, which uses suicide bombings as its signature attack.

Police Brig. Gen. Sarhad Qadir, who gave the casualty figures, said the dead included at least five women and three children. About 120 people were wounded.