Security is being stepped up in Los Angeles, its area airports and other parts of Southern California amid new Daesh-related threats calling for attacks on uniformed personnel, several U.S. officials told NBC News on Friday.

Daesh, which controls swathes of Syria and Iraq, has long called on its sympathizers to attack Western interests around the world.

Los Angeles had already started using two-man patrols as a precaution. Upgraded measures were extended to Los Angeles International Airport this week, officials said.

Investigators said there was no specific plot but concerns increased as a result of intelligence from overseas as well as ongoing monitoring of suspected radicals inside the United States. FBI Director Jim Comey has said investigations into suspected Daesh sympathizers are underway in all 50 states.