Washington, May 15 (PTI) : ISIS has declared a state of emergency in their de-facto capital of Raqqa in Syria, a US official has said while asserting that the dreaded terror network is feeling "threatened".

"We have seen this declaration of emergency in Raqqa, whatever that means," Colonel Steve Warren, the spokesman for the US-led anti-ISIS coalition, was quoted as saying by CNN.

"We know this enemy feels threatened, as they should," he said.

US 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, the report said.

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.

"We've had reports of ISIL repositioning both their combat capabilities, I guess what they think may be coming next," Warren said, using another name for ISIS.

"And we've seen reports of them repositioning personnel ... either within the city or even out of the city."

US military also notes that the movement of fighters who have been well dug in throughout Raqqa could give overhead surveillance aircraft an improved chance of finding and targeting them.

And while the US has not officially said it believes ISIS leader Abu Bakr Al-Baghdadi still remains in or around Raqqa, several officials say that has continued to be a working assumption.

However, they are monitoring any potential intelligence that he could be in other locations as well.

"Baghdadi remains extremely careful" about his personal security, a US defence official was quoted as saying.

The US will continue to try to find him, the official said. But even if he is located and captured or killed, the US assessment is that it would not immediately change the scope and capability of ISIS operations, because there are other leaders ready to step in.