According to army and medical sources, the attack took place on Wednesday when an assailant rammed his explosives-laden vehicle into a gathering of Shia volunteers around 20 kilometers (12 miles) south of the city of Tikrit.
An army lieutenant colonel said the deadly assault also left 13 other people, including five civilians, injured.
No one immediately claimed responsibility for the explosion. However, during the past few days violence has increased between pro-government forces and the ISIL south of Tikrit and around Samarra.
The Iraqi military, Kurdish Peshmerga forces and Shia volunteers have managed to push ISIL terrorists out of some of their positions in the eastern part of the country.
The Takfiri militants, who control Tikrit and have positions around Samarra, have carried out numerous attacks around both cities to pressure pro-government forces.
The Wednesday attack came as according to an unnamed local official, the ISIL militants took control of the area of Dejla, north of Samarra, in the same day. Dejla is a main supply route for government forces near Samarra.
The ISIL militants currently control parts of Syria and Iraq, where they have been committing heinous crimes in the captured areas, including the mass execution of civilians and security forces.
Iraqi authorities have repeatedly blamed Saudi Arabia and a number of Riyadh’s Persian Gulf allies for extending financial and logistical support to the terror campaign in Iraq.