Some of Italy's most popular tourists sites were named by the State Department on Thursday as "potential targets" for terrorist attacks, as ISIS renewed its separate threat to America.
The U.S. Embassy in Rome identified the Vatican's St. Peter's Basilica, the Duomo and La Scala theater in Milan, and "general venues" like churches, synagogues, restaurants, theaters and hotels as locations possibly at-risk.
"Terrorist groups may possibly utilize similar methods used in the recent Paris attacks," the message to American citizens added. "The Italian authorities are aware of these threats."
Americans were advised to stay vigilant, monitor local media and "factor updated information into personal travel plans and activities."
It came as ISIS separately released another propaganda video warning President Barack Obama that it would carry out attacks against Americans. The video was verified by NBC News terror analysts, Flashpoint.
In an interview with state broadcaster RAI Thursday, Italy's Foreign Minister Paolo Gentiloni also said St. Peter's Basilica and the Duomo and La Scala could be targets, adding that the country's security services were looking for five possible suspects.
Italy raised its security alert level to 2, the highest possible in the absence of a direct attack on the country, following the attacks in Paris on Friday.