(CNN)ISIS appears to have gained more ground in Iraq. Islamic State fighters surrounded one of Iraq's largest air bases Tuesday, a police captain in Anbar province and other security sources told CNN. The militants are preparing to launch an attack on Ein Al-Assad military airbase, which is halfway between Hit and Haditha, said Anbar police Capt. Omar Mohamad Hanin. Anbar has been largely overrun by ISIS, which has been waging war for months in order to establish a caliphate -- or a society run by strict Sharia law. It has also taken over large swaths of Syria, near the border with Turkey.
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John Kerry says Turkey is on board with coalition fighting ISIS
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President Obama says effort to destroy ISIS will have ups and downs
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Iraqi police captain, sources: ISIS has surrounded one of Iraq's largest air bases
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ISIS continues its assault on Syria's Kobani; coalition fights back with airstrikes
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