The operation took place in a night raid in Naples between Sept. 4 and Sept. 5 and France has filed a request for extradition of the 24-year-old suspect, who was of North African origin and considered dangerous, the sources said.
“In France, he is accused of participating in subversive activities,” one source said.
There was no word on whether the man was linked to any immediate threat but news of the arrest coincides with a heightened alert over security in western Europe.
Last month, French authorities said they had received news that a suicide bomber was preparing to attack the Paris metro system and Western intelligence sources also said they had uncovered plans for a coordinated attack on European cities.
Police declined to give details of the Naples arrest but the sources said he had been under observation since late August and computer materials had been seized from the place where he was staying in the city center.
Elements in the Naples investigation linked the arrested man, identified only as R.H., to the possible use of explosives, one source said.
“He had equipment that could be used to measure out commercially available components that would allow the construction of a bomb similar to the one at the Santa Barbara barracks in Milan,” the source said.
In 2005, a Libyan man threw a homemade bomb at the army barracks in Milan, losing a hand in the explosion and slightly injuring a soldier.
Intelligence reports and arrests show militant groups linked to Al-Qaeda, especially in North Africa, have been active in Italy, mostly recruiting and financing for attacks planned elsewhere in Europe.
Italian troops are stationed in Afghanistan and Lebanon, but Italy pulled out of Iraq in 2006. “Our hypothesis is that he came to Italy to recruit and train others and to pick up false documents and weapons as other individuals we have investigated have,” one of the sources said.