Rebels fighting for an al-Qaeda affiliate are challenging government control for a region that includes the country’s most important oil refinery.
After days of intense battles, there were “conflicting reports of who controls Baiji, a town north of Baghdad and home to Iraq’s largest refinery,” Reuters said.
Mosul, Iraq’s second city, was already controlled Tuesday by fighters of the Islamic State in Iraq and the Levant.
The insurgents wants to replace Shiite rule from Baghdad in Sunni-majority regions of the country.
Prime Minister Nouri al-Maliki leads the country’s Shiite central government.
Iraq is OPEC’s second-biggest oil producer.
The Baiji refinery has a capacity of up to 310,000 barrels of oil a day.