NOC's chief of operations, Saad al-Karbalaie, was killed in the northern oil city of Kirkuk. Gunmen forced him to stop his vehicle as he was leaving his office and then shot him, Reuters quoted police sources as saying.
There was no immediate claim of responsibility for the attack on Karbalaie, who was supervising production and export facilities in Kirkuk.
Major oil producer and Opec member Iraq faces security challenges from the ultra-hardline Sunni Islamic State which controls a third of the country, and a sectarian conflict exacerbated by the group's presence.
Baiji
