Investigators suspect members of the Badr Organization paramilitary group conducted a small but steady smuggling operation at a makeshift military base south of Kirkuk.

In territory that was ostensibly liberated two years ago, security forces, civilians, and energy infrastructure have become regular targets of an intensifying IS guerrilla war.

After encountering heightened security on the outskirts of Basra, near the Rumaila oil field, two suicide attackers blew up their car bombs.

Iraqi premier claims members of Kurdish police were involved, raising prospect of political motives behind the May 2 attack.

The attack echoes a series of assassinations targeting northern oil officials in 2015.