Los Angeles (CNN) Federal counterterrorism officials are warning police departments across the country to maintain a heightened state of awareness for the potential for ambush-style attacks against officers.

In a new intelligence report viewed by CNN, entitled "PERSISTENT THREAT OF TERRORIST AMBUSH ATTACKS ON FIRST RESPONDERS," analysts from the National Counterterrorism Center warn that police officers and emergency services personnel remain key targets for terrorists, who may either seek to lure public safety officers into ambushes, or stage ambush attacks without significant advanced planning.

Philadelphia police block an intersection on August 14, 2019. A suspect shot at least six Philadelphia police officers, with gunfire continuing for more than one hour.

"Due to their high visibility and 24/7 accessibility, on-duty first responders are susceptible to becoming victims of ambush attacks," states the report issued this week.

The intelligence report states that the appeal of ambush-style attacks for terrorists "likely stems from the nature of the target, the attack concealment, and the element of surprise." It also indicates "the suddenness of an ambush attack may limit reaction and response by first responders, potentially providing the attacker with a tactical advantage."

Citing FBI data, the report indicates that 53 US law enforcement officers were the victims of ambush-style attacks by both terrorist and non-terrorist suspects between 2014 and 2018.

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