Police in Italy have arrested five people on suspicion of plotting to attack a church in the northern city of Bologna. The arrests follow reports in the Italian media this summer that the al-Qaeda terrorist network was planning to bomb the basilica.

The men, one Italian and four Moroccans, were detained after being seen filming in and around the San Petronio basilica in Bologna.

The church is one of Italy's finest examples of Gothic architecture and contains a 15th century fresco interpreted by some Muslims to be offensive. The work depicts the prophet Mohammed being devoured by demons in hell.

The men said they were tourists, but investigators say they have recordings that prove the men were discussing a possible terrorist attack on the church. Investigators have made public a transcript of the conversation in the Berber language inside the church.

One of the group is reported to have said that if the painting was not removed then "we will bring the whole thing down."

Another voice on the recording is reported to have said: "What bin Laden does is what needs doing here."

The men were arrested Monday by plainclothes paramilitary police, after having videotaped the painting and central altar of the basilica.

Investigators also said that the men had planned to return to the church early in the morning. They said the men appeared nervous and had said they should leave before being discovered.

Security has been tight at the basilica since last June when Italian investigators declared they had broken up a Milan-based terror cell with links to Osama bin Laden's al-Qaida network. Officials said the group was planning an attack on the church.

Since September 11, Italy has cracked down on terrorism with a series of operations against groups allegedly related to al-Qaida.