Police have arrested 15 people in raids across north Italy who they accuse of belonging to a far-left group linked to the Red Brigades guerrilla movement.
Milan and Turin were among the cities where raids took place
The arrests had probably foiled an attack, Italy's Interior Minister Giuliano Amato said.
The original Red Brigades carried out many acts of violence in Italy in the 1970s and 1980s, including the 1978 kidnap and murder of ex-PM Aldo Moro.
The group fell silent for a decade but an offshoot emerged in the late 1990s.
Monday's operation included sweeps in Milan, Turin, Padua and Trieste, the police said.
Those detained were accused of subversive association and forming an armed gang, a police statement said.
They had been under investigation since 2004, police said.
"Probably, this time we succeeded in preventing a Brigades attack," Mr Amato said.
Italian media reported that among the alleged targets were a house in Milan belonging to former Prime Minister Silvio Berlusconi and the headquarters of his Mediaset broadcaster.
Reports said investigators had found video footage of some of the suspects training with firearms.