Abusive chants were hurled by AC Milan supporters against southern club Napoli.
During Sunday's match against Juventus in Turin, hundreds of Milan supporters shouted "We are not Neapolitans", a chant the Naples daily Il Mattino said reflected long-standing contempt for the south by northern clubs.
In the fiercely territorial world of Italian soccer, abusive rivalry between supporters of clubs in the rich north and those in the poorer south is not uncommon and Milan officials reacted with shock to the verdict by Serie A sporting judges.
"To say I'm furious would be putting it mildly," Milan chief executive Adriano Galliani told reporters. "I understand that racism is a big problem, a problem everywhere in the world, but territorial discrimination is another thing entirely."
The sentence means that Milan, in 12th place in the Serie A standings after a 3-2 loss to Juventus on Sunday, will play its next home game on October 19 against Udinese behind closed doors.
The Serie A sporting judges also banned Milan defender Philippe Mexes for four matches for violent conduct after video evidence showed him punching Juventus player Giorgio Chiellini as Juventus was taking a corner.
The punch was not seen by the referee but Mexes was sent off with a second yellow card. – Reuters