WASHINGTON (AFP) - The United States authorities on Wednesday (Dec 16) added a new "bulletin" category to the national terror-alert system, aimed at communicating intelligence on lower-level threats to American citizens.
The country implemented an alert system in 2001 to communicate threats to the public, under two categories: elevated and imminent.
But the Department of Homeland Security had yet to issue any alerts under the system, because the threat level never rose sufficiently to warrant it.
Under the new system, the lower-level category of "bulletin" will be used for "describing broader or more general trends and current developments regarding threats of terrorism", the DHS said.
The agency issued its first bulletin on Wednesday (Dec 16), which will stay in effect until June 16 next year.
While the authorities stressed there remains no credible, specific terror threat to the United States, the bulletin warns of a "new phase in the global threat environment". It states: "Particularly with the rise in use by terrorist groups of the Internet to inspire and recruit, we are concerned about the 'self-radicalised' actor(s) who could strike with little or no notice."
Homeland Security Secretary Jeh Johnson also said that immigration officers are increasingly scouring social networks to glean information on some visa applicants.
"We've begun to consult social media with regard to certain immigration benefits. We began that very early this year. I think we need to do more of this," he told reporters.
The US authorities are on edge in the wake of the San Bernardino mass shooting on Dec 2. The FBI is investigating this as a terrorist attack.
The attack, carried out by Syed Farook and his wife Tashfeen Malik, left 14 people dead.
FBI director James Comey told the US media the two had exchanged private messages in late 2013 "showing signs in that communication of their joint commitment to jihad and to martyrdom".
But he said that, despite reports to the contrary, there was no evidence the pair posted public messages supporting terror on social media at that time - something that could have alerted investigators to their intentions.