Five Nigerians were detained in Brescia and in the southern town of Aversa, near Naples, police said. A sixth Nigerian already jailed in Turin for other crimes was served an additional arrest warrant, police said.
The six suspects comprise the "cupola," or the top decision-makers, of the "eiye" mob group, said Carmine Grassi, the Brescia police official in charge of the operation.
Like their Sicilian counterparts, the mobsters protected their territory by striking back violently at other Nigerian-run criminal organizations, police said.
Police displayed an ax and knife they said were used against rivals, sometimes to amputate body parts.
Initiation rites included drinking blood as part of a "blood pact," Grassi said. Members also had to wear blue hats and blue shoes, and used slang and hand gestures that distinguished them from other gangs, police said.
Grassi said the alleged leaders met while attending university in Nigeria.