Giuseppe Governale, the chief of Italy's Special Operations Group (Ros), said that while there was “constant monitoring of those people who operate clandestinely and become radicalized” this “does not eliminate the risks”.
“No one is able to eliminate them,” he was quoted by Ansa as saying.
His comments came on Thursday, as he announced a police sting on a European ‘jihadist network' that was allegedly planning to kidnap diplomats and carry out attacks to try to spring its leader out of detention in Norway.
Seventeen arrest warrants were issued and 13 people were detained in Italy, Britain and Norway, according to Eurojust, the EU's Judicial Cooperation Unit.
The other wanted suspects were believed to be fighting in Iraq or Syria for the Isis group, Governale said.
The year-long Jubilee of Mercy gets underway on December 8th and is expected to bring millions of Catholic pilgrims to Rome - a city which has faced persistent threats of attack by Isis.
Italy has been on heightened alert since an Isis video earlier this year warned that Libya could be used as a springboard for attacks in the country.
Read more: Could Isis terrorists really invade Italy?
Giampiero Massolo, the chief of the Department of Security Information (Dis) said “the higher level of exposure the higher the risk”.
"However there are no specific attacks planned that we know about. We are concerned but not alarmed," he was quoted by Ansa as saying.
"The greatest threat is presented by lone wolves, individual actions, people who become radicalized in the privacy of their own home and then, perhaps with a few friends, carry out terror attacks.”
Among those arrested on Thursday was Abdul Rahman Nauroz, whom police said was “particularly active in recruitment activities” with his apartment in the northern Italian city of Merano being used as a “place for secret meetings and a crossroads for aspiring jihadists”.