ISIS issues latest threat against Vatican.

US intelligence services have warned Italy that St Peter's Basilica in Rome, as well as Milan's Duomo and La Scala opera house, have been identified as "potential targets" for terrorist attacks, along with churches, synagogues, restaurants, theatres and hotels.

RAI state radio reported that the FBI has passed the information to the Italian government which has already heightened security in Rome in recent days.

On 19 November the US Embassy in Rome emailed a "security message” to US citizens in Italy, stating that "terrorist groups may possibly utilize similar methods used in the recent Paris attacks", and urging US citizens to "remain vigilant and aware of their surroundings."

The security threat comes as Rome prepares for the Vatican's Holy Jubilee Year of Mercy which begins on 8 December and is expected to attract millions of extra pilgrims to the Italian capital.

Rome's increased security measures also come as the latest issue of ISIS magazine Dabiq contains a new threat to attack St Peter's.

Although security has been doubled at the Vatican, Pope Francis said at his general audience on 18 November that he was against installing "reinforced doors" at churches.