Story highlights US officials are closely watching the situation

Reports that ISIS fears its capital could be attacked

(CNN) U.S. military officials are closely watching social media and news reports that say ISIS believes it may soon come under siege in Raqqa, Syria, its self-declared capital.

"We have seen this declaration of emergency in Raqqa, whatever that means," Col. Steve Warren, the spokesman for the U.S.-led anti-ISIS coalition, told reporters Friday. "We know this enemy feels threatened, as they should."

Photos: Life inside Raqqa In this photo from November 29, 2015, provided to CNN by the activist group Raqqa is Being Slaughtered Silently, residents assess the damage to a building in the northern Syrian city -- ISIS's headquarters -- which has been the target of French airstrikes in recent weeks. Hide Caption 1 of 8 Photos: Life inside Raqqa In this photo from November 6, 2015, an ISIS fighter walks along a street in Raqqa with his 3 wives walking behind him, according to RBSS. Hide Caption 2 of 8 Photos: Life inside Raqqa A child looks at a stand selling military fatigues in Raqqa on October 1, 2013. Many in Raqqa say they don't want to live under ISIS but have no choice. Hide Caption 3 of 8 Photos: Life inside Raqqa Men look at a large black jihadist flag in Raqqa on September 28, 2013. In Raqqa today, school is banned -- and even small pleasures, like chocolate, are an unaffordable luxury because many cannot work. Hide Caption 4 of 8 Photos: Life inside Raqqa A Syrian man mourns the deaths of six of his siblings, killed in a bomb attack during fighting between rebel fighters and Syrian government forces in Raqqa on August 10, 2013. Hide Caption 5 of 8 Photos: Life inside Raqqa A man carries two children away from the scene of an explosion in Raqqa on August 7, 2013. Hide Caption 6 of 8 Photos: Life inside Raqqa In this undated photo, provided to CNN by RBSS, you can see normal life in Raqqa -- once one of Syria's most liberal cities -- before the start of the civil war. Hide Caption 7 of 8 Photos: Life inside Raqqa The streets of Raqqa before it was under ISIS control, in an undated photo provided to CNN by RBSS. Hide Caption 8 of 8

Media reports have indicated that ISIS is moving personnel around the city and trying to put up covers in certain areas to shield potential targets from airstrikes and ground attacks.

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"They see the Syrian Democratic Forces, along with the Syrian Arab Coalition, maneuver both to their east and to their west," Warren said. "Both of these areas becoming increasingly secure, and the Syrian Democratic Forces increasingly able to generate their own combat power in those areas."

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