Warning signs Islamic State threat grows amid online calls for jihad

The Islamic State (IS) threat on the US homeland has caused renewed concern as more details emerged about the man allegedly behind what the FBI is calling an "act of terrorism" in New Orleans on New Year's Day that killed 14 and injured scores more.

- Ben Makuch

US citizen and army veteran Shamsud-Din Jabbar, 42, was killed in the attack after driving into partygoers on Bourbon Street and engaging police in a gunfight. Found inside his rental truck was the black flag of IS; it was later revealed he had pledged allegiance to the group in a series of videos posted to Facebook mere hours beforehand.

Though public perceptions of IS suggest it has now suddenly reappeared in the pantheon of terrorist organisations active in the US, top officials and analysts have been warning for months that a stateside attack was imminent.

"The attack was hardly unexpected - there had been flashing warning signs," said Clara Broekaert, a research fellow at the Soufan Center who tracks the online activities of IS. "In recent months, we've witnessed an unrelenting stream of rhetoric calling for violence during the holiday season, along with repeated chatter about low-tech tactics, from knife attacks to vehicle rammings. Given this, it's no shock that an attack like this occurred."

Both the outgoing FBI director, Christopher Wray, and the attorney general, Merrick Garland, called IS an ongoing and top national security concern in an October press release. In a rare public acknowledgment, the CIA director, Bill Burns, recently described IS as "resurgent", a description now underscored by political chaos in Syria.

Since the summer, IS propaganda has steadily called for American targets to be "next" as a presidential election campaign rife with unprecedented political violence and assassination attempts bogged down law enforcement and intelligence attention.