Italy, the subject of several internet threats from purported Islamic militant groups, said it had begun expulsion procedures against 701 people.
"The latest evaluations ... confirm an ongoing high risk of a terrorist attack on our country," the ministry said in a statement after a parliamentary meeting on the findings from a series of nationwide raids in recent days.
Italy has not been attacked by on its home soil, but after bombings in July in London and the Egyptian resort of Sharm-al-Shaikh most Italians fear it is only a matter of time before they are hit.
Italy, like Britain a close ally of the United States, has sent 3000 troops to Iraq.
Beefing up security
Officials have boosted security on Italy's transport system. Nearly 33,000 people had been questioned in recent days as part of the nationwide investigation that involved all branches of Italy's security and police forces, the ministry said.
Owners of money transfer agencies, call centres and internet cafes had been investigated and two of the people arrested were brought in under newly approved anti-terror laws, it added.
"The latest evaluations confirm an ongoing high risk of a terrorist attack on our country"
Interior Ministry statement
Parliament last month passed measures that give the Italian state greater powers to combat terrorism after Interior Minister Giuseppe Pisanu said terrorists were "knocking on Italy's door".
The package makes it easier for police to detain and deport suspects, increases penalties for terror-related crimes and gives approval for greater surveillance of internet and telephone traffic.
Some critics argue the measures impinge on civil liberties, while others, including some commentators close to the centre-right coalition, have voiced concern Italy is not prepared to deal with the aftermath of an attack.
The ministry said in September there would be a trial run of emergency procedures in several areas of the country. Italy in the past has named Rome, Milan, Vatican City and towns such as Florence and Venice as potential targets.