Police officials say the attack took place today afternoon when the bomber drove his explosives-laden truck into a checkpoint manned by Shiite militias near the city of Tikrit.
At least 15 Shiite fighters were also wounded in the attack.
Tikrit, which fell under the control of the Islamic State group last summer, is 130 kilometres (80 miles) north of Baghdad.
Medical officials confirmed the casualties. All officials spoke on condition of anonymity because they were not authorised to talk to the media.
