One person was confirmed dead and about 200 others were injured in Naples during the fan’s celebratory party for winning the Seria A title 33 years ago.
It is not yet clear if the shots were fired as part of the football celebrations, or if it was criminal activity, according to the Corriere della Sera daily.
La Stampa newspaper said the victim, who died after being taken to hospital, was linked to a local mafia clan. Police are investigating.
More than 200 people ended up in hospital overnight for injuries sustained during the celebrations, La Stampa said, from knife wounds to burns from firecrackers and asthma attacks caused by inhaling smoke from flares.
Napoli’s 1-1 draw at Udinese on Thursday evening secured their third league title, and their first in 33 years, with a record-equalling five games to play.
Thousands of fans in Udine, at the Stadio Maradona in Naples and all around southern Italy’s biggest city exploded with joy at the final whistle.