U.S. Official: Iraq's Anbar vulnerable to ISIS

(CNN) – ISIS fighters are taking control of more and more key parts of the Syrian border city of Kobani, and a United Nations envoy tells Reuters that thousands of people "will most likely be massacred" if the city falls.

Human rights groups say Islamic extremists now control almost half the city – including the governmental square and the surrounding security zone. ISIS released a video that reportedly shows its forces inside Kobani, fighting Kurdish and Free Syrian Army forces. CNN has not independently confirmed the authenticity of the video.

Meantime on the other front of the war, Iraq, sources tell CNN that they are concerned that Anbar province, just west of Baghdad, could soon fall to ISIS too.

CNN's Jim Sciutto reports.