Story highlights US-backed troops continue to close the net around ISIS' self-declared capital

ISIS has occupied the Syrian city since 2013

(CNN) Civilians in Raqqa faced uncertainty after ISIS ordered the evacuation of the Syrian city, and then rescinded the command.

Residents began to flee the city Sunday and take to higher ground after ISIS issued a statement warning of the expected collapse of the Euphrates Dam, according to local activist group Raqqa is Being Slaughtered Silently (RBSS).

RBSS said ISIS later announced via loudspeaker that the dam was fine and requested residents remain in the city.

Raqqa is the latest city targeted by coalition forces in their attempts to rid Iraq and Syria of the extremist group. The city, which is is the extremist group's operational command headquarters, is now largely surrounded -- its main supply routes cut off by advancing forces.

The activist RBSS posted videos that purport to show Raqqa civilians fleeing, with groups of people clamoring to leave the city by car and foot. It also posted pictures that allegedly show coalition aircraft targeting the dam, which would endanger the northern Syrian city should it fail.

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