Former Barcelona star Luis Figo has called for more to be done to tackle football hooliganism in the wake of the violence that has marred Euro 2016 in France.
He made the comments at an economic conference in St Petersburg in Russia - whose most extreme fans have launched a series of thuggish attacks on England supporters during the tournament.
Many England supporters have also been arrested following clashes with French police in recent days.
The retired footballer, who won a record 127 caps for Portugal, told a panel discussion at the St Petersburg International Economic Forum that he cannot understand what drives some fans to violence.
Speaking in English, he said: "The most important thing from my point of view in terms of sports is that the sport has some values that probably some people don't understand because they never try it or they never live with these values.
"And the violence in football is something that all the stakeholders that are here have to fight against because it is not part of the sport - the violence.
"I don't understand the people who go to a stadium, go to an event, to fight. It's probably because they don't belong to this industry, for sure."
He said politicians and sports governing bodies should consider calling off tournaments that erupt in violence.
He told the forum: "Not only the police and security, but I think all the people who are involved in this business have to be alert and fight against this kind of situation.
"It is no example for no one, and for of course our kids, the youngest who have a dream in this business to achieve some goals."
He added: "Sometimes I think you have to stop - I don't know which way because I'm not the person who should decide if it is the government, UEFA, FIFA... to give (an) example that the violence and this kind of attitude should not happen in football, or in any sport in the world."
Russia have been issued with a final warning and fined 150,000 euros (?120,000) by UEFA after some of their fans charged and attacked English supporters following their opening match in Marseille.
There have been other reports of hardened Russian 'ultras' ambushing and beating up England fans in French streets.
England have also been warned they could be kicked out of the tournament following violence among some of their supporters.
Several have been jailed in France for their role in the clashes.
French streets have resembled a battlefield at times as police armed with batons, tear gas and pepper spray have been engaged in running battles with fans.