FBI warning came after a publicly available list of US churches was posted on a militant social media site
Federal authorities warned local law enforcement authorities across the US on Friday that Islamic State sympathizers were continuing to call for attacks on churches and other holiday gathering sites.
As they did so, President-elect Donald Trump used Twitter to broadcast his potentially inflammatory thoughts on the truck attack on a Berlin Christmas market on Monday.
Isis militants claimed responsibility for the attack, in which 12 people died and 56 were injured, but did not offer proof. The suspect in the attack, a Tunisian national, was shot dead in Italy on Friday.
Trump wrote: The terrorist who killed so many people in Germany said just before crime, by Gods will we will slaughter you pigs, I swear, we will slaughter you.
This is a purely religious threat, which turned into reality. Such hatred! When will the US, and all countries, fight back?
The federal US warning was issued after a publicly available list of US churches was posted on a militant social media site.
As part of the continuous dialogue with our law enforcement partners, the FBI routinely shares information about potential threats to better enable law enforcement to protect the communities they serve, FBI spokesman Andrew Ames said.
Ames added that citizens were advised to maintain awareness of their surroundings and report suspicious activity.
The FBI is aware of the recent link published online that urges attacks against US churches. As with similar threats, the FBI is tracking this matter while we investigate its credibility, he said.
We continue to work closely with our federal, state and local law enforcement partners should there be any potential threat to public safety.
Separately on Friday, police in Australia detained five men suspected of planning a series of Christmas Day attacks using explosives, knives and a gun in the heart of Melbourne.