Story highlights Iraq's military leaves an important military base in Anbar province to ISIS, sources say

The base is a key control point for roads through the region, where ISIS is advancing

CNN team on the Turkey-Syria border describe fierce fighting for the city of Kobani

A Kurdish fighter said it would be "impossible" to hold ground if current conditions continued

Baghdad (CNN) Iraq's military abandoned a strategically important base in Anbar province after heavy fighting with ISIS militants, provincial security force sources told CNN on Monday.

The base outside the city of Hit was one of the Shiite-led government's few remaining military outposts in Anbar, a predominantly Sunni province that has increasingly fallen under ISIS control.

It is a key control point for roads running through the region.

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The Iraqi military still controls the Ayn al-Asad military base, which helps defend Iraq's second-largest dam and the provincial capital of Ramadi.

Despite airstrikes by the U.S. and its allies over the weekend, reports suggest ISIS has continued to gain ground and has encircled Haditha, the last large town in Anbar not yet in the militant group's hands.

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