Italian investigators say they have discovered plans for an attack on a church in Bologna by Islamic extremists linked to Osama bin Laden's al-Qaida organization. They say the attack was to have been carried out by a Milan-based terrorist cell.

The Italian investigators say they learned of the planned attack on the basilica of San Petronio in Bologna through telephone interceptions. A major investigation into Muslim extremists operating in Italy has been underway since the September 11 terrorist assaults on the United States.

According to a report in the Italian daily Corriere della Sera, the Bologna church was targeted because it contains a 15th century fresco depicting Islam's Prophet Mohammed in hell, being devoured by demons.

A group of Italian Muslims had appealed to the Vatican last year to have the fresco by Giovanni da Modena removed, arguing that it offended Islam, but nothing was done. The Union of Muslims on Sunday denied any link to the alleged plot against the Bologna church.

According to the newspaper report, telephone interceptions by Italy's Carabinieri police indicated that, starting in February, members of a Milan cell began plotting the attack on orders of Salafist leader Hassan Hattab. Specific details were not disclosed.

Authorities said the tapped conversations were between several Tunisians and Moroccans with links to a Libyan identified only as Amsa and considered one of Osama bin Laden's chief operatives in Europe. Corriere della Sera said Amsa, who was living in Milan at the time, was arrested in Britain last month.

Amsa is believed to have been coordinating Islamic cells in a number of European countries, including Italy, Spain, Belgium and Britain. Italian investigators also are said to have intercepted conversations in which he discussed a possible attack on the U.S. Embassy in Amsterdam.

The Italian investigation into the Milan-based terror cell led to the arrest and conviction of seven Tunisians earlier this year. They were accused of providing logistical support to al-Qaida members passing through Europe.