An Islamic State attack on a state-run gas plant in Baghdad's northern outskirts on Sunday killed at least 11 people, including policemen, and forced two power stations it supplied to suspend electricity production.
A suicide car bomb went off at the entrance of the facility in Taji at around 0600 local time (0300 GMT), allowing another vehicle carrying at least six attackers with explosive vests to enter and clash with security forces, police sources said. Twenty-one people were also wounded.
The militant group said in an online statement that four fighters with machine guns had killed the guards at the plant which it said the Iraqi army was using as a headquarters.
When reinforcements arrived, they set off a parked car bomb before clashing with the security forces and detonating their suicide vests.