The fighting erupted on Friday evening between the terrorist Islamic State of Iraq and the Levant (ISIL) and the so-called Army of the Men of the Naqshbandiyah Order (JRTN) in Hawija, in Kirkuk province, said the sources on Saturday.
There were differing accounts as to what sparked the firefight, which is a potential sign of the fraying of the Takfiri insurgent alliance that has overrun some parts of territory north of Baghdad in less than two weeks.
One security official said JRTN insurgents had refused an ISIL demand to give up their weapons and pledge allegiance to the terrorist group.
Witnesses, however, told AFP the two sides clashed over who would take over multiple fuel tankers in the area.
Analysts have noted that while the Takfiri insurgents, who are led by ISIL but also include a litany of other groups including loyalists of executed dictator Saddam Hussein, have formed a wide alliance, it is unclear if the broader grouping can hold together given their disparate ideologies.
ISIL, which is seen as the most dangerous terrorist group in Iraq, has for months clashed with groups opposed to the Syrian government, where it also operates and where it is seen as far more extremist than even Al-Qaeda's front terrorist group in the country, known as al-Nusra Front.
NTJ/MB