The bomber detonated explosives inside a Kurdish restaurant about 10 km (6 miles) north of Kirkuk, said Major General Jamal Tahir, police chief of Kirkuk.
Tahir said the restaurant was packed during lunch hour. Many Iraqis are on holiday during Eid al-Adha, a four-day religious holiday, and would be more likely to visit restaurants.
Iraqi and American security forces sealed off the area following the bombing, a Reuters reporter said.
Violence has dropped sharply in Iraq over the past year, but militants still stage attacks on a routine basis. Thursday's bomb attack was the deadliest in months.
Photo: Hurriyet Archives