The Italian Football Federation (FIGC) has suspended all matches indefinitely after a policeman was killed at a Serie A match between Catania and Palermo.
A supporter is injured during the violence at the Stadio Massimino
Officer Filippo Raciti died as violence flared during the Sicilian derby.
The FIGC has called off all this weekend's professional and amateur games, and also cancelled Italy's friendly with Romania on Wednesday.
Commissioner Luca Pancalli said: "What we're witnessing has nothing to do with soccer, so Italian soccer is stopping."
According to reports, 38-year-old Raciti was struck in the face by a small explosive while attempting to deal with fighting outside the stadium.
He was taken to hospital but died from his injuries.
Pancalli had warned earlier this week that more violence would bring a halt to league matches after clashes between supporters and police in several cities last Sunday.
"One day is not sufficient," Pancalli added after proceeding with his threat. "Without drastic measures, we cannot play again.
"We will immediately set up a commission to discuss the situation between sport and politics. It's not possible to carry on like this."
Catania, fifth in Serie A, against Palermo, who are third, was given an early kick-off time on Friday because of fears over public safety.
Prior to the start, a minute's silence had been held following the death of a club official from lower league club Sammartinese last weekend.
We need a strong and clear signal to avoid the degeneration of this sport
Italian prime minister Romano Prodi
But the match was suspended after an hour when tear gas, used by police to break up the fighting outside the ground, drifted onto the field.
The fighting, reported ANSA news agency, was because Palermo fans could not get into Catania's Stadio Massimino until the second half.
The two teams fled the pitch for the dressing-room, with the game suspended for 30 minutes.
After the match, fans continued to fight running battles with police on the streets outside the stadium and around a hundred people were treated for injuries, while dozens with lesser injuries were taken to local hospitals.
Another police officer is also believed to be in a critical condition.
Catania club executive Pietro Lo Monaco reacted to news of the officer's death by announcing he would leave football.
"I've heard that a policeman has died," he said. "To speak of football right now seems useless. For me this is the end. I will leave the football world.
Palermo's players try to get away from the tear gas
"I don't recognise myself in this world anymore. I have loved football intensely but after this right now it seems absurd."
Palermo coach Francesco Guidolin was quick to blame Catania fans for the violence.
"We won the match, but we cannot enjoy this victory," said Guidolin. "Football cannot last for much longer like this. There will be no joy in it."
The Catania prosecutor's office has announced an investigation into the incident.
England head coach Steve McClaren reacted to the news by insisting the FIGC must now make the same harsh decisions made in Britain 20 years ago to eradicate football violence.
"They have got to learn a lot about the English game, how it has come on over the years," McClaren told BBC Radio Five Live.
"The safety at most grounds has improved. It is all very, very well controlled and is a great environment in which to take families, and we have to encourage that.
"A lot of other countries are looking at the way we built stadiums, our security, seating and ticketing arrangements and maybe after the drastic events in Italy something has to be done."
Italian prime minister Romano Prodi also issued a statement.
"After the serious incidents that occurred tonight in Catania, my first thought is for the people that have been affected and for their families," he said.
"I feel a duty to say that we need a strong and clear signal to avoid the degeneration of this sport which we are seeing more dramatically and more often."
Palermo had taken the lead through Andrea Caracciolo, but Catania equalised within 60 seconds of the teams coming back out thanks to Fabio Caserta.
Palermo won the game with a controversial David di Michele goal in the 83rd minute.