The most deadly was in oil-rich Kirkuk, where explosives hidden in a parked car killed three Kurdish soldiers in a passing convoy, said police Brig. Anwar Qadir.
At least 12 others were wounded in the blast, he said. All the victims were members of the Kurdish peshmerga forces, guarding a police chief traveling from Sulaimaniyah to the east, Qadir said.
Kirkuk is an ethnically mixed city near Iraq's semiautonomous Kurdish region, about 290 kilometers (180 miles) north of Baghdad. The area has seen a spike in violence in recent months, which U.S. military officials attribute to the northward flow of militants after American offensives in Baghdad and its surrounding belts.
Farther north in Mosul, police said another parked car bomb missed a passing police convoy but killed a civilian instead. The explosion wounded seven others, including a police officer, and damaged several storefronts.
Mosul lies 360 kilometers (225 miles) northwest of the Iraqi capital.