Kobani is still holding out against ISIS, the top Kurdish official in the besieged Syria border city said Monday – but a senior U.S. defense official warned that American air strikes may not be enough to save it from falling to militants. Fighter jets are unable to launch strikes at potential targets inside Kobani because it is difficult to differentiate between ISIS or Kurdish fighters and because of the potential for the killing of innocent civilians, the U.S. official said, adding that "there is concern that Kobani could still fall" to ISIS.

U.S. military forces launched eight air strikes against ISIS outside Kobani on Sunday and early Monday, U.S. Central Command (Centcom) announced in a briefing.

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"Our fighters are still heroically resisting [ISIS],” Anwar Muslim, the top Kurdish official inside Kobani, told NBC News, "They control about 30 to 35 percent of the city on the eastern side. Our fighting, along with the US and coalition airstrikes, are holding off the ISIS assault." He said ISIS has tried "four or five” times to take new territory by sending in car bombs, but so far the attempts have been unsuccessful. "Our men and women fighters are using Kalashnikovs and light weapons, but they are still fighting against ISIS which is using all forms of weapons it took from the Iraqi army in Mosul.”

Muslim added that ISIS continues to have strongholds south and east of Kobani and that the humanitarian situation in the city is grave. He called for a humanitarian corridor to be opened on the Turkish border to allow access for relief supplies. Secretary of State John Kerry last week said the he was “deeply concerned” by the city’s plight but cautioned that the U.S. had wider strategic objectives in the fight against ISIS.

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Anwar Muslim, the top Kurdish official in Kobani, told @NBCNews the city is still holding out against the ISIS assault. - Richard Engel (@RichardEngel) October 13, 2014

ISIS has tried “4 or 5” times to take new territory in Kobani by sending in car bombs, so far without success, Kurdish official said - Richard Engel (@RichardEngel) October 13, 2014

- Richard Engel, Jim Miklaszewski, Courtney Kube and Alastair Jamieson