ISIS News Today 2015 Update: Extremist Group Claims Control of Iraq's Biggest Oil Refinery

The Islamic State claimed that part of Iraq's largest oil refinery is now under its control, posting images online on Sunday to back up its assertion.

The Islamist extremists claimed they launched an attack on the Baiji oil refinery late Saturday. The next day, the group said its fighters entered the site and took control of a number of buildings, CNN reported.

The Iraqi government denied the claim, maintaining that government forces are still in control of the site.

The ISIS posted pictures in a number of websites allegedly showing an attack on the facility, with plumes of smoke rising in the air above the contested oil refinery.

The claim could not be verified by CNN, but it would not be the first time that militants and government forces clashed over the refinery, which processes much of the fuel used by Iraqis locally.

The refinery is a "key strategic resource that has long been a lucrative target," the CNN report said. "If an attack damaged oil fields or machinery, it could have a significant impact."

In 2011, at least four armed gunmen attacked the Baiji oil refinery, killing two engineers and two technicians. They also planted about 10 bombs around one of the refinery's production units, with the explosion creating a huge fire and leaving damage that took two years to repair.

By then, the refinery produced 150,000 barrels per day of gasoline, benzene and kerosene.

The site is only 40 km from the northern Iraqi city of Tikrit, seized by the Iraqi forces and Shiite militias from ISIS less than two weeks ago. U.S.-led airstrikes targeted ISIS positions around the city, which had been in the hands of ISIS since June. Such airstrikes paved the way for Iraqi forces to move into Tikrit.

Pockets of clashes, however, still continue elsewhere, with both government forces and militia united in clearing operations.