KIRKUK, Iraq - Islamic State militants ambushed a convoy of government-backed militia fighters near the northern Iraqi city of Kirkuk late on Sunday, killing at least 12 of them, police and militia commanders said on Monday.At least 10 other fighters from the Popular Mobilization Forces (PMF) are missing, a local militia commander said.A security official said Iraqi security forces were pursuing the Islamic State militants who disguised themselves in police uniforms to carry out the attack."Daesh ambushed the PMF convoy, making use of the bad and rainy weather. At least 10 fighters are still missing. We fear Daesh might execute them." said Abbas al-Jabouri, a local PMF commander, referring to Islamic State by an Arabic acronym.Iraqi forces launched an operation this month to consolidate control of a mountain area near the oil city of Kirkuk to be used for the transit of Iraqi oil, highlighting concern about mountainous terrain where two armed groups are active.Iraq declared victory in December over Islamic State militants who seized control of nearly a third of the country in 2014. However, the group continues to carry out attacks and bombings in Baghdad and different parts of the country.