ROME (AFP/REUTERS) - Italy is looking for five terror suspects after a tip-off from the FBI about possible militant attacks on landmark sites including St Peter's cathedral in the Vatican, Foreign Minister Paolo Gentiloni said on Thursday (Nov 19).

"Since yesterday afternoon, our security forces have been working to find five people," Mr Gentiloni told the Raitre television station, reiterating that the country was already primed for the possibility of an attack on St Peter's or other historic monuments such as La Scala theatre in Milan.

"The minister of the interior has explained many times that we are at a very high level of alert covering symbolic sites, places where people gather, from stadiums to cathedrals, and St Peter's in particular, which were, among others, the places highlighted by the FBI yesterday," Mr Gentiloni said.

"We always take such signals of alarm very seriously, especially when they come from the United States."

With the FBI alert plastered all over Italy's front pages on Thursday, the minister appealed for calm.

"We must not become prisoners of this alarm because that would be a gift to Daesh," he said, using the Arabic name for the Islamic State in Iraq and Syria (ISIS).

Italy raised its security alert level to 2, the highest possible in the absence of a direct attack on the country, following Friday's attacks in Paris in which Islamic State gunmen and bombers killed 129 people.

Mr Gentiloni said the US embassy in Rome had recommended tourists take particular care in certain parts of Italy, but had not advised them against going there.