New York (Reuters): US federal officials warned local law enforcement to be aware that supporters of Islamic State have been calling for their sympathizers to attack holiday gatherings in the United States, including churches, a law enforcement official reported.

The warning was issued in a bulletin to local law enforcement, stated there were no known specific, potential threats.

The notice from the Federal Bureau of Investigation and Department of Homeland Security was issued out of an abundance of caution after a publicly available list of U.S. churches was published on pro-Islamic State websites.

The FBI said in a statement “The FBI is aware of the recent link published online that urges attacks against U.S. churches. As with similar threats, the FBI is tracking this matter while we investigate its credibility.”

Islamic State sympathizers “continue aspiration calls for attacks on holiday gatherings, including targeting churches.” The notice describes different signs of suspicious activity for which police should be alert, it said.