Christimas celebration in New York
People take photos at the Dyker Heights Christmas Lights in the Dyker Heights neighborhood of Brooklyn, New York City, Dec. 23, 2016. REUTERS/Andrew Kelly

Federal officials warned law enforcement authorities across the U.S. on Friday that supporters of the Islamic State group, also known as ISIS, "continue aspirational calls for attacks on holiday gatherings, including targeting churches."

Authorities have advised people to exercise caution and report any suspicious activity, FBI spokesman Andrew Ames said, according to the Associated Press. FBI will work closely with federal, state and local law enforcement in case of any likelihood of such attacks.

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

The warning follows postings on ISIS channels on Telegram app calling on the militant group’s supporters to carry out attacks across churches in all states in the U.S. during the holiday season. The posts listing addresses of churches were reportedly uploaded by a user named “Abu Marya al-Iraqi.”

The Telegram post was in Arabic and called on “for bloody celebrations in the Christian New Year.” It also said it planned to use the militant group’s network of lone-wolf attackers to “turn the Christian New Year into a bloody horror movie.”

Another post reportedly urged ISIS sympathizers to attack churches, popular hotels, crowded coffee shops, streets, markets and public places, and published a list of addresses for these places in the U.S., Canada, France and the Netherlands.

Recently, the SITE Intelligence Group also cited similar ISIS posts. Officials in the U.S. have beefed up security across the country during the holiday season following Monday’s attack in Berlin, where a man drove a truck into a Christmas market killing 12 people. ISIS claimed the attack and called the suspect — identified as Anis Amri — a “soldier of the Islamic State.” Amri, a 24-year-old Tunisian, was killed in a police shootout in Milan, Italy, on Friday after a Europe-wide manhunt was launched for him.