Italy's football authorities have ordered AC Milan to play its next game behind closed doors and fined the club 50,000 euros following abusive chants by 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...here in Italy we have invented territorial discrimination for ourselves
"I called (Italian football) president (Giancarlo) Abete to ask whether he thinks that this rule is just. What I ask is that it is abolished."
A spokesman from the football federation (FIGC) said the rules were being applied in line with UEFA guidelines.
"It's not as though the rules are imposed on any club. It's down to a judge to decide on the punishment, and they can make their case against any decision," the spokesman said.
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 for a second yellow card.