The militants this week entered the Unesco World Heritage site of Palmyra after seizing the town near the ancient ruins.
Pictures emerged on Thursday purporting to show the decapitated bodies of men killed by the group in the city.
Isis is now thought to control about half of Syria. The group also recently captured Ramadi in Iraq and has vowed to take control of Baghdad and Karbala.
“The Italian government is worried not only about what's happening in Syria but also about the maybe more threatening situation in Iraq,” Foreign Minister Paolo Gentiloni told La Repubblica.
He added that the anti-Isis coalition will soon meet in Paris to discuss strategy.
"It will be fundamentally important to verify the strategy that we move forward with."
The extremists have claimed their fighters are already in Europe. Persistent threats have been made against Italy, particularly Rome, the centre of the Catholic Church.
Pictures emerged on Twitter last week purporting to show supporters holding up signs at several Rome landmarks and train stations declaring the group's presence in the capital.
The images were circulated just a few days after the Omar al Gawari, the information minister for Libya's internationally-recognized government based in the port city of Tobruk, warned the group would be heading to Italy “in the coming weeks".
Italian authorities came under fire this week after it emerged that a Moroccan man suspected of being involved in the deadly attack on Tunisia's Bardo museum in March arrived in Italy aboard a migrant boat.
But analysts played down the threat, saying it is unlikely the jihadis would risk their lives making the treacherous crossing.