File - In this Monday, Oct. 6, 2003 file photo, an abandoned watchtower and lines of barbed wire are seen surrounding Iraq's largest oil refinery as smoke rises from a petroleum gas flare, in the city of Beiji, north of Baghdad. On Wednesday, June 18, 2014, a top Iraqi security official said Islamic militants of the al-Qaida-inspired Islamic State of Iraq and the Levant laid siege to Iraq's largest oil refinery late Tuesday night, threatening a facility key to the country's domestic supplies as part of their ongoing lightning offensive across the country. The Beiji refinery accounts for a little more than a quarter of the country's entire refining capacity and any lengthy outage at Beiji risks long lines at the gas pump and electricity shortages, adding to the chaos already facing Iraq. (AP Photo/Ivan Sekretarev, File)
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