The New York City Police Department (NYPD) and other law enforcement personnel responded to a threat from the Sunni militant group Islamic State (IS) after someone re-released an old message that tells followers to "rise up and kill law enforcement officers".
The threat specifically named the US, France, Australia and Canada as targets, CNN reported.
NYPD employees were told in an internal memo to "remain alert and consider tactics at all times while on patrol", especially in light of the attacks in France last week.
The Federal Bureau of Investigation and the US Department of Homeland Security issued a similar bulletin to law enforcement agencies across the country.
That bulletin and the NYPD memo makes it clear that this new message is consistent with previous threats that IS and others, including the Al Qaeda, have issued.
John Miller, NYPD deputy-commissioner for counterterrorism, tempered fears of a threat to officials in New York City.
"I don't think that we are under any more threat, or any less threat than we were the day before," he said in a television interview.
Miller said that the department was on a "heightened security posture on a normal day compared to almost any other police department".
More than 1,000 police officers and civilian analysts are assigned to a counter-terrorism mission everyday and officers have studied the recent attacks in France, he said.
France was hit with three days of terror after three suspects killed 17 civilians in multiple attacks last week.
"IS appears to be renewing or recycling previous threats made in an audio tape released by IS spokesman Abu Mohammed al Adnani in September which called for attacks by supporters on France and other Western countries in retaliation for air strikes in Syria and Iraq," the report said.
Miller said, however, that the video re-release showed that the IS was using the momentum from the Paris attacks in part of their messaging strategy to see "who can we get to follow this".
The killing spree began in Paris, France, Wednesday at the offices of Charlie Hebdo, a satirical magazine, after two brothers stormed the building, killing 12 and later escaping.
Early Thursday, a female police officer was killed after a suspect dressed in all black and wearing bulletproof vests shot her in a Paris suburb.
Two hostage situations unfolded Friday between law enforcement and the two sets of suspects. The first scene ended with the two brothers suspected of the magazine murders killed by security forces.
At the same time, authorities moved into a Jewish grocery store where hostages were being held by the alleged cop-killer. While 15 hostages escaped, four were killed, as well as the suspect.
