Hussein Abs Hamir, 29, a self-proclaimed member of the Islamic State jihadist group made the remark during an intercepted phone conversation with this his sister, according to investigators in the port city of Crotone.
Hamir faces charges of conspiracy to commit international terrorism and criminal association, police said.
Investigators said they found a photo of Crotone's police chief Claudio Sanfilippo and other police officials on Hamir's mobile phone and believe he visited Rome in recent months to recce security in the capital.
Hamir recruited other asylum-seekers at Crotone's migrant shelter to IS, incited them to carry "violent acts aimed at terrorism" and gave them updates and propaganda materials on IS, according to police.
Magistrates said Hamir exalted the nail bombing that killed 23 adults and children and wounded 119 people in Manchester last month after a concert by US singer Ariana Grande - an attack claimed by IS.
"In the presence of other guests at the shelter he watched and listened to videos of the Manchester attack on May 22, gloating about the attack and repeatedly uttering the phrase 'Allah Akbar' (God is Great)," wrote investigating magistrates in Crotone in their warrant for Hamir's arrest.
"He also watched and listened daily to IS jihadist videos with the volume turned up high," the warrant added.
Hamir repeatedly said he had no qualms about belonging to IS, claiming the group was "good" and that "for me it is God".
Hamir's arrest came after a "complex and lengthy" probe coordinated by anti-mafia prosecutors in Catanzaro and by counter-terrorism police in Crotone, investigators said, describing him as "a violent individual with strong criminal inclinations".
He entered Italy in August 2009 as an illegal boat migrant and previously requested asylum in Norway in 2008, in Finland in 2009, and in Germany and Denmark in 2010, according to police.
Half a million people, many of them Muslims from North Africa and the Middle East, have reached Europe via Italy in the past three years, and boat arrivals are up more than 17 percent this year from 2016.
Hamir's case will intensify searing political debate on Italy's citizenship laws and the
management of boat migrants ahead of national polls due by next May.
(This story has not been edited by Social News XYZ staff and is auto-generated from a syndicated feed.)
About VDC
Doraiah Chowdary Vundavally is a Software engineer at VTech . He is the news editor of SocialNews.XYZ and Freelance writer-contributes Telugu and English Columns on Films, Politics, and Gossips. He is the primary contributor for South Cinema Section of SocialNews.XYZ. His mission is to help to develop SocialNews.XYZ into a News website that has no bias or judgement towards any.