According to Yahoo.fr, the man is accused of belonging to Al-Qaeda and was arrested in Naples. Sources of the investigation have said he is of North African origins, knows how to build bombs and is 24-year-old. France has asked for his extradition because he is accused of "subversive activities" in the country.

Italian police has not released much more information about his arrest, except that his initials are R.H. and that he was in possession of "equipment which could serve to measure the components to make an explosive similar to the one which went off in Santa Barbara in Milan". Back in 2005, a Libyan national throw an home-made explosive device against that building, hurting a soldier.

Intelligence have shown that Muslim activists linked to Al-Qaeda, particularly to its groups in North Africa, are active in Italy, where they are recruiting and funding attacks against Europe.

Meanwhile, US has issued a travel warning to all US nationals travelling to Europe regarding the credible but inspecific threat. There is no country specially singled out, but rather the warning is for the whole of Europe. It is mainly to advise US nationals to take care while in tourist areas.

Background:
US: Europe can be attacked Mumbai style.
Credible threat to Europe.
Sweden raises terrorism threat level.
Concern about terror cells' being ready to strike in Europe.