Clashes have been reported between Iraqi forces and Iraqi Kurdish fighters after Baghdad sent troops towards Kurdish-held sites in Kirkuk province, the BBC reports.
State TV report that Iraqi forces have taken control of some areas, including oil fields, “without fighting”, but Kurdish officials deny this.
An exchange of artillery fire is said to have occurred south of Kirkuk city.
Tensions between the two sides over the future of Iraqi Kurdistan have been high since Iraqi Kurds voted for independence in a September referendum.
Kirkuk is not part of the autonomous Iraqi Kurdistan region.