Iraq's largest oil refinery was attacked Wednesday by Sunni militants using machine guns and mortars, according to media reports. The attack on the Baiji refinery in northern Iraq began at 4 a.m. local time, the BBC reported. The refinery, located roughly 50 miles north of Tikrit, on Tuesday was shut down overnight and staff evacuated after members of the Islamic State of Iraq and Syria, or ISIS, threatened an attack, Reuters reported.

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