The attack in the disputed city of Khanaqin came as Iraqi electoral officials prepare to release the first official preliminary returns from Saturday's vote for provincial councils.
Kurdish and police officials who gave the casualty toll said most of the victims in Thursday's blasts were Kurds who had been lunching at the popular Abu Dalshad restaurant.
The city's police chief Col. Azad Eisa said 15 other people were wounded in the attack.
Khanaqin, 90 miles northeast of Baghdad, has been a source of friction between Kurds and the Arab-run central government. Hundreds of Kurds complained on election day that they couldn't find their names on voter registration lists.
Salahuddin Kokha, an official with the local chapter of a Kurdish political party, said the attack was meant to upset Kurdish claims of a strong showing in elections in mainly Sunni Diyala province.
"Terrorists want to destroy the happiness of the Kurds over their election victory in Khanaqin," Kokha said. "All of those killed were civilians."
Official results from Saturday's balloting, which took place in 14 of the country's 18 provinces, were to be announced at 5 p.m. (9 a.m. EST) Thursday in Baghdad.
But early returns leaked by political parties have led to allegations of irregularities in several provinces, particularly Anbar province, a former insurgent stronghold west of the capital.
Tensions between rival Sunni parties have been running high in Anbar, causing Iraqi authorities to ask U.S. troops to stand by in case of trouble following Thursday's elections announcement.
A leader of the Awakening Councils - Sunni tribesmen who turned against al Qaeda in the area - has complained that the rival Iraqi Islamic Party had stolen the election for members of the ruling provincial council. The IIP denies the charge.
Maj. Gen. Tariq Yousif, chief of the provincial police, said he had asked U.S. troops to patrol outside the cities in case of trouble.
"The American troops are deploying now in Anbar province," Yousif told The Associated Press by telephone. "We have an agreement with the American troops to support us in case of any emergency."
The U.S. military did not respond to a request for comment.
Anbar, once the main front in the Sunni insurgency, was handed over to Iraqi control last year but U.S. Marines remain there in support of the Iraqis.
The Awakening Councils ran their own lists of candidates in the Saturday election, saying they deserved political power because they drove al Qaeda from the province.
On Wednesday, a top leader of the Awakening Councils, Sheik Ahmed Abu Risha, told Al-Arabiya television his group had "hundreds of documents" to prove the number of votes was inflated in Anbar to throw the election to the Islamic Party, which controls the provincial administration and is part of the national government.
Voting in Anbar and elsewhere in the country took place without major violence. But U.S. and Iraqi officials fear there could be trouble if the losers don't accept the results. Elections will be held later in four northern provinces, three of them in the Kurdish self-governing region.
Also Thursday, a roadside bomb targeted a Shiite candidate for provincial election in Baqouba, northwest of Baghdad, an Iraqi police officer said.
Salim al-Zeidi escaped injury when the bomb exploded outside his home, said the officer, who spoke on condition of anonymity because he was not authorized to release the information.
In a separate attack, a roadside bomb targeted a government convoy that was carrying a deputy education minister.
Ministry spokesman Waleed Hussein said the bomb exploded Thursday morning as the convoy passed through the Baghdad neighborhood of Mansour. He said deputy education minister Muadh al-Jibouri escaped injury.