(CHICAGO.CBSLOCAL) — Over the past six years, Chicago has become a top potential target for international terrorists, a top security expert said Friday, making the posting of a veiled threat by Islamic radicals on Twitter a higher cause for concern.

“Many terror organizations refer to Chicago as Obama Town,” said CBS 2 security expert Ross Rice, a former FBI agent in Chicago. Under President Obama, the U.S. took out Osama bin Laden, and used repeated drone strikes to weaken terror networks.

In the meantime, the U.S. government on Friday issued a security bulletin to all U.S. law enforcement in light of the overall threat posed by Islamic State, commonly known as ISIS or ISIL.

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