Six Islamic State suicide attackers forced their way into a natural gas facility north of Baghdad on Sunday, triggering a gun battle that set three gas storage units ablaze, security forces said.
The six militants entered the Taji plant in the early morning with an explosive-rigged car but were shot dead by guards, said General Saad Maan, spokesman of the Baghdad Operations Command.
Other security officials and witnesses said that five people were killed and 14 injured in the attack.
Another group of attackers then engaged in a shoot-out with security guards at the plant, leading three gas reservoirs to catch fire, Maan said, adding that firefighters were tackling the blaze.
Islamic State supporters on social media circulated a newsflash purportedly from the group's Aaamaq news agency, which said that commandos from the extremist organization had stormed the plant.
Islamic State has also claimed responsibility for a wave of bombings that killed more than 90 people in Baghdad on Wednesday.
The group, which controls wide areas of Sunni-populated northern and western Iraq, frequently bombs busy civilian targets such as markets and restaurants in mainly Shiite areas of the capital.