The imam and asylum seeker, from Somalia, was detained at a refugee centre near the city of Campobasso after a two-month investigation during which he was recorded saying “let's start from Italy, let's go to Rome and start with the station”.
He was also heard saying that “Charlie Hebdo was just the beginning, the war continues”, Corriere reported.
Investigators believe he was planning to leave the refugee centre in Campomarino on Wednesday and head to Rome.
The man is said to have supported the Isis extremist group and tried to encourage migrants staying at the centre in Campomarino to join the jihadist cause.
Police said the imam, who also praised the November 13th Paris attacks, held services in the centre, but that some worshippers walked out after being alarmed by his preaching.
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Police used phone tapping and hidden cameras during their two-month investigation. The camera showed the man watching videos of terrorist attacks, police said.