US bolsters security at military bases over terror threat

The US military has bolstered security at bases across the country as a precaution after the FBI voiced concern that Islamist extremists could target troops or police officers, officials said Friday.

The head of US Northern Command, Admiral William Gortney, ordered the heightened alert to make sure troops have a "greater awareness and vigilance out in the field" for potential security risks, a defense official told AFP.

"We want to make sure they're taking extra care guarding installations and our people," said the official, who spoke on condition of anonymity.

The move raised the official alert status one notch higher on a five-point scale, from the fourth level "Alpha" to the third level "Bravo," which the military describes as an "increased and predictable threat of terrorism."

Officials said most of the additional security measures would likely not be readily apparent to the public, apart from perhaps more bags being searched at base entrances.

The move came after two men attempted to storm an exhibition on Sunday showing caricatures of the Prophet Mohammed in a Dallas suburb. The two heavily-armed gunmen were shot dead by a local police officer before they could approach the building where the event was being held.

Pentagon chief Ashton Carter said Thursday the two assailants had been "inspired" -- but not directed -- by the Islamic State group to stage the failed attack.

FBI Director James Comey reportedly said on Thursday authorities were concerned about the IS encouraging attacks on "the uniformed military and law enforcement" via online propaganda.

There are "hundreds, maybe thousands" of people in the United States who had received recruitment messages from the jihadists, Comey said.

The risk posed by IS-inspired homegrown militants was "a factor in the decision" to raise the security level but not the only factor, defense officials said.

The FBI chief's comments echoed warnings from lawmakers and experts Thursday who said the IS group's social media efforts are carried out on a vast scale and at a tempo that Western governments are unable to keep up with.

The IS has 2,000 people tweeting for the group 150 times a day, according to J.M. Berger, an author and fellow at the Brookings Institution think tank.

The group's innovative and aggressive approach online has given it "an unprecedented level of success" compared to other extremist organizations, said Berger, who has tracked IS activity in social media.