A bomb blast on Monday killed at least 15 people and wounded 170 others at a Kurdish rally in the northern disputed city of Kirkuk, a police official said.
"We are still investigating if the explosion was carried out by a female suicide bomber or caused by an explosive device," said Maj. Gen. Jamal Tahir of Kirkuk police.
Tahir said police also detonated a car bomb in Kirkuk about one kilometer (less than 1 mile) away from the site of the first explosion, which occurred when demonstrators gathered to protest a provincial elections law that is being debated in parliament.
Kurdish objections over a proposed power-sharing formula on the provincial council in Kirkuk have blocked the law from being passed.
Iraq's Sunni parliament speaker, Mahmoud al-Mashadani, was hospitalized on Monday after fainting at the beginning of a session on Kirkuk. He was in stable condition after suffering a sharp drop in blood pressure, his office said.
Kirkuk is in an oil-rich area and many Kurds consider it to be part of their historical land. The area is home to Kurds, Turkomen, Arabs and smaller groups.
After Monday's explosion, dozens of angry Kurds opened fire on the offices of a Turkomen political party, which opposes Kurdish claims on Kirkuk.
A police official, speaking on condition of anonymity because he was not authorized to speak to the media, said no one was hurt in the attack and that the party offices were placed under police protection.
The attack in Kirkuk coincided with bombings in Baghdad on Monday that left at least 28 people dead during a Shiite pilgrimage.