The attack occurred in Khalis, 50 miles north of Baghdad, a police officer said on condition of anonymity out of concern for his own safety. Ten Iraqi soldiers and five civilians were wounded, the officer said.
The city is located in Diyala province, which has seen some of the worst violence recently as mostly Sunni militants are believed to have fled to the area since U.S. and Iraqi troops launched a security crackdown in Baghdad on Feb. 14.
Earlier Thursday two suicide bombers attacked an office of the Kurdistan Democratic Party of Massoud Barzani, leader of the autonomous Kurdish region in Iraq, killing three of its guards and wounding five, police said.
The casualties could have been higher if guards had not opened fire on the two attackers, one in a car followed by another in a truck, forcing them to detonate their explosives at least 50 yards from the office, police said.
The attack occurred in Zumar, a town that is 45 miles west of Mosul, the capital of Ninevah province.
It was the second suicide attack this week aimed at the KDP in that area.
Across Iraq on Wednesday, 45 people died in attacks by suspected insurgents or militias, including four police officers who were killed when a suicide bomber struck a police station in Balad Ruz, also in Diyala province.
Also Wednesday, the U.S. military said an American soldier died the day before in a non-combat related incident. No further details were released.
Two days earlier, a double truck-bombing killed nine U.S. soldiers in the volatile province. An al Qaeda-linked group claimed responsibility for the attack.
On Thursday, a funeral procession was held in Baghdad's Shiite neighborhood of Sadr City for an Iraqi who locals said was killed in an attack by the U.S. Air Force early that morning. Associated Press Television News footage showed three large craters in the ground of the commercial area and the windows of some of its stores had been blown out.
The U.S. military said it was checking the report, but could not immediately confirm it.
On Wednesday, radical Shiite cleric Muqtada al-Sadr joined growing criticism of a 3-mile-long, 12-foot-high concrete wall the U.S. military is building in Azamiyah, a Sunni stronghold of Baghdad that has been targeted by mortar and rocket attacks by Shiite militiamen. Al-Sadr called the wall a "sectarian, racist and unjust" plot by the Americans to divide Iraqis.
Al-Sadr supporters demonstrated in Sadr City, chanting "No, no to division."
Others carried a banner that read, "the building of the Baghdad wall is the beginning of Baghdad's division."
Al-Sadr's Mahdi militia has been blamed for much of the sectarian bloodshed the U.S. says the Azamiyah wall is designed to stop.
Nonetheless, an al-Sadr aide, Sheik Salah al-Obaidi, told reporters in the Shiite holy city of Najaf that other demonstrations were planned in Baghdad to condemn the wall. He said that if security permits, al-Sadr's followers would like to join Sunni demonstrators in Azamiyah.
Al-Sadr, apparently seeking to shore up his political support, has been trying to make overtures to the Sunni minority while distinguishing between ordinary Sunnis and extremists who target Shiites.
The U.S. military has said al-Sadr is in neighboring Iran, despite insistence by his aides that he is in hiding in Iraq. Al-Obaidi said al-Sadr was in hiding "for security reasons" and that "it is not necessary to know where he is."
In other developments: