Islamic State has urged followers to attack the US, and the attorney general has called the group a top security concern

The Islamic State (IS) threat on the US homeland has caused renewed concern as more details emerge 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.

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 infamous 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.