Napoli condemned on Monday "so-called supporters" who caused chaos on a major Italian motorway at the weekend by fighting with fans from rival club Roma.
Napoli fans were travelling to Genoa to see their team beat Sampdoria 4-0, while Roma supporters were on their way to AC Milan where their team drew 2-2.
Hardcore "ultra" supporters of both teams were involved in serious clashes on the A1 motorway on Sunday afternoon after they bumped into each other at the Badia al Pino service station in Tuscany.
Nicknamed the "sunshine motorway", the A1 runs from Naples to Rome and then all the way to Milan in northern Italy.
"Napoli strongly condemns the behaviour by so-called supporters, who unfortunately still attend football matches in Italy, which involved creating disruption and danger for true fans," Serie A leaders Napoli said in a statement.
"They also struck fear into people who had nothing to do with football on the A1 motorway."
Videos posted on social media by public broadcaster RAI show dozens of supporters fighting with flares, belts and bats as police sirens blare in the background.
Italian media report police as saying that the running battles led to the motorway being blocked for 50 minutes, creating queues up to 15 kilometres long.
"It was a crazy act which put in serious danger people travelling on one of the country's most important roads," Roberto Rossi, chief public prosecutor in Arezzo, was quoted as saying.
Napoli highlighted how football hooliganism in England has been reduced since the 1980s, calling on the Italian government "to swiftly take appropriate measures of a radical nature".
"It is unacceptable for violent people to travel across Italy and attend stadiums without any consequences," added Napoli.
Football Federation chief Gabriele Gravina decried as "shameful what happened", adding that "institutions can and must do more".
"These people have nothing to do with sport and should be punished," he said.
Football violence is nowhere near as widespread in Italy as it was in the past but on occasion high-profile clashes between fans put the issue back in the headlines.
In December 2018 a fan was killed by a passing van during a huge battle between Inter Milan and Napoli fans just a few minutes walk from the San Siro.