Giovagnoli, in a telephone interview with The Associated Press, said the five men, arrested on Monday in San Petronio Basilica, were accused of criminal association with the aim of terrorism. The arrests were made by plainclothes paramilitary police who were assigned to basilica two months ago.
In June Milan daily Corriere della Sera reported in June that extremists were plotting to attack the basilica because the fresco depicts Islam's prophet Muhammad in Hell, being devoured by demons.
The five men, who live in the province of Padua, a city in northeast Italy, were arrested after they filmed, with a videocamera, the fresco and the central altar with ancient crucifix, and were overheard saying worrisome things, Giovagnoli said. "They were heard saying phrases hostile to (the Christian) religion, expressing the possibility of destroying" religious symbols, Giovagnoli said.
The men were heard saying: "That which (Osama) bin Laden does is just what's needed," according to the prosecutor. Another phrase was: "If they don't take it (the fresco) away, everything will come tumbling down," Giovagnoli said. The men also said: "We need to return early, at 7:30 in the morning," Giovagnoli said. "We're not sure if that meant they wanted to be in the church when it first opens when no one is there or if they wanted to mix in during a religious service" soon after the church opens.
Carabinieri Col. Luigi Finelli, interviewed on private Canale 5 news, said the men also said: "Let's get out of here before we're be discovered." Authorities did not immediately release the men's names.
Last year, a group of Italian Muslims appealed unsuccessfully to the Vatican to have the fresco, by Giovanni da Modena, removed or parts of it covered, arguing that it offended Islam. Corriere della Sera had reported that Carabinieri paramilitary police learned of the plot by intercepting phone conversations as part of a larger investigation into Muslim extremists operating in Italy.
That investigation led to the convictions earlier this year of seven Tunisians in Milan who were accused of providing logistical support to recruits of al-Qaida, bin Laden's terrorist network, passing through Europe.
The Tunisians were also accused by prosecutors of links to the Salafist Group for Call and Combat, a dissident faction of the Armed Islamic Group, Algeria's most radical insurgency movement. The United States has branded the Salafist group a terrorist organization and ordered its assets frozen.
The wiretaps indicated that starting in February, members of the Milan cell began plotting an attack on the Bologna church on orders of Salafist leader Hassan Hattab, Corriere said. Specific details, however, were never discussed.
Asked if the Bologna authorities had uncovered any links between the five men and suspected terrorist cells in other Italian cities, Giovagnoli said so far nothing has turned up to indicate a connection.