This was reported by the newspaper "Corriere della Sera" (Friday), citing an investigation by "Il Piccolo".
According to the report, the 46-year-old is now in a prison in Trieste following his arrest by Interpol in the Netherlands.
A suitcase containing a handgun and ammunition was found there shortly before Pope Francis' visit in July 2024.
The man is said to be connected to this and the suspected attack was planned by a Turkish organisation linked to IS.
The day after the unexplained incident, the Pope had celebrated an open-air service in the main square of the harbour city of Trieste in north-eastern Italy.
He used an open electric vehicle to get around.
A short time later it became known that the Italian police were investigating possible plans for an attack.