The suicide attack occurred at about 8:30 pm in a cafe in the outdoor market in Tuz Khormato, a mostly Turkomen city 210 km north of Baghdad.
Turkomen, one of Iraq’s ethnic main groups, follow both the Sunni and Shi’ite traditions of Islam.
Witnesses said the blast was so powerful that it collapsed the ceiling of the one-storey cafe, burying many of the victims.
Hours after the blast, rescuers were still sifting through the debris
looking for the dead or injured.
Authorities used mosque loudspeakers to appeal for blood donations.
In Baghdad, gunmen seized a senior Iraqi Oil Ministry official in the second high-profile kidnapping in the Iraqi capital in as many days.
Attackers stopped Adel Kazzaz, director of the North Oil Co, shortly after he left the Oil Ministry in eastern Baghdad, ministry spokesman Assem Jihad said.
Gunmen who seized up to 31 people in a daylight raid on a Baghdad club on Saturday released six of their hostages yesterday.
There was no word on the other hostages, including the Olympic National Committee chairman, Ahmed al-Hijiya.
British soldier killed
Elsewhere in Iraq up to 26 Iraqis were killed, as well as a British soldier, in a variety of incidents.
The British military said the soldier was killed and another wounded during a raid against “terrorist suspects” in Basra.
British troops arrested a top Shi’ite militia leader, Sajid Badir, leader of Mahdi Army in the city, Iraqi police said, but it was unclear if the two events were linked.
The US military said an American soldier was also killed in a roadside bombing in south Baghdad, but no further details were released.
Gunmen also swooped on the detention wing of the main hospital in Baqouba, 55 km north-east of Baghdad, and freed 13 prisoners under treatment there.
Four policemen were killed in the assault and three prisoners were later recaptured.
Elsewhere, a suicide bomber attacked a joint US-Iraqi patrol in the northern city of Mosul, killing three civilians and wounding six others, including two women, police said. Three construction workers were also shot dead.
In Baghdad, a bomb hidden in a trash bag exploded in a commercial area of the Karradah district, killing four people and wounding 21 others, while one person was killed and two were wounded when a bomb exploded near a police patrol in north Baghdad.
Two people were killed and five were wounded in a gunbattle between police and militants in another north Baghdad neighbourhood.
In the northern city of Kirkuk, two barbers were killed in a drive-by shooting, police said. Drive-by shootings killed one person in Mosul and another in Muqdadiyah, north-east of the capital.
In Diyala, a former official of ousted president Saddam Hussein’s Baath party was killed in a drive-by shooting along with his son and a woman bystander.