The US State Department has issued a travel warning for Americans visiting Italy due to terrorism.

The warning, issued on Dec. 31, advises Americans to "exercise increased caution in Italy."

"Terrorist groups continue plotting possible attacks in Italy," the warning reads. "Terrorists may attack with little or no warning, targeting tourist locations, transportation hubs, markets/shopping malls, local government facilities, hotels, clubs, restaurants, places of worship, parks, major sporting and cultural events, educational institutions, airports, and other public areas."

Earlier in December, Italy's top anti-terrorism prosecutor said that stopping lone wolf attacks was a top priority for the government "because we no longer have a structure that is directly governed and directed by a center of international terrorism, but we have lone wolves."

Italy is also focused on protecting ancient monuments in Rome, such as the Colosseum, from vandalism and terrorism.

"It’s not just about vandalism," reported iNews. "The culture minister, Alberto Bonisoli, and Ms Russo announced the €7m (£6.3m) security upgrade just days before a Somali national was arrested for allegedly plotting to bomb St Peter’s Basilica and other Italian churches."

"ISIS has blatantly threatened to strike the Colosseum more than once."

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