Four suspects were arrested in the latest anti-terror raid while two more are said to still be on the run.
All are suspected of being part of a jihadi plot to strike the headquarters of the Roman Catholic Church – where the Pope spends much of his time – as well as the Israeli embassy.
Among them is a kickboxing champion who was sent his orders for an attack on the Italian capital via mobile messaging service Whatsapp.
Abderrahim Moutaharrik, 28, was arrested on Thursday along with his wife Salma Bencharki, 26.
Investigators believe the couple were preparing to take their two young children to Syria.
Police also detained Moroccan Abderrahmane Khachia, 22, and female suspect Wafa Koraichi, 23.
The extremist cell was planning to carry out atrocities in Italy with “particular attention to the city of Rome”, Milan prosecutor Maurizio Romanelli said.
He said Rome was being targeted “because it is a destination for Christian pilgrims”.
Prosecutors released an image of Moutaharrik wearing his kickboxing uniform along with a traditional Middle Eastern headdress and ISIS branded t-shirt.
The jihadi suspect is an Italian national of Moroccan descent who has competed in kickboxing championships across Europe.
He was crowned Switzerland’s welterweight national champion for 2013 and 2014.
One of the messages to Moutahrrik said: “Dear brother Abderrahim, I send you… the bomb poem… listen to the sheik and strike.”
Italian interior minister Angelino Alfano said the group had “very bad intentions” after wire-tapped phone conversations revealed plans “to hit Israel in Rome”.
The transcript said: “I swear I will be the first to attack them in this Italy of crusaders, I swear I’ll attack it, in the Vatican God willing.”
Italian authorities are now looking for a 39-year-old Italian woman, Alice Brignoli, who changed her name to Aisha, and her husband Mohamed Korachi.
Both are thought to have left Italy last year for ISIS territory in Syria.