By Caroline Wyatt
BBC News, Paris
French football clubs and the authorities have vowed to clamp down on football hooliganism in France after a lethal confrontation between police and supporters of the Paris Saint-Germain team.
Violence followed the French's side defeat by the Israeli visitors
Some 100 supporters of the team chased a Jewish man, shouting racist and anti-Semitic slogans, after their side lost 4-2 to Hapoel Tel Aviv last Thursday.
A black plain-clothes police officer who tried to protect the French fan of the visiting Israeli team also became the focus of the crowd's anger.
When he too came under verbal and physical attack, he drew his gun amid the chaos and shot and killed one Paris Saint-Germain supporter and seriously injured another.
France was horrified by the picture of football-related violence, racism and anti-Semitism revealed by the tragic incident.
The Paris prosecutor must now decide whether the police officer, Antoine Granomort, acted in legitimate self-defence or whether charges should be laid.
At the same time, the Tel Aviv fan, Yaniv Hazout, and his family are being given increased protection measures by the local authorities in the tough Paris suburb of Sarcelles in case of reprisal attacks.
A police trade union official, Luc Poignant, has defended Mr Granomort's action.
He said the crowd was shouting "filthy Jew" at Mr Hazout, and when they saw the plain-clothes policeman, who is of Afro-Caribbean descent, they began to yell: "Filthy black, we're going to get you."
Police have said they will clamp down on hooliganism
Witnesses say they also saw PSG fans give Nazi salutes and heard them make monkey noises.
The Interior Minister, Nicolas Sarkozy - known for his hardline stance on law and order - says France will do everything it can to stop racist fans entering football stadiums.
The Socialist party has also suggested looking to the UK for examples of how to act successfully to prevent football hooliganism.
Mr Sarkozy held a crisis meeting on Saturday with the head of the French Professional Football League, whose president Frederic Thiriez said he was "shattered" by what had happened after Thursday's game, and would do all he could to ensure such an incident could never take place again.
But the director-general of the French police, Michel Gaudin, insisted that recent measures taken against football hooliganism had already begun to have an effect.
He told Le Parisien newspaper that violent racist acts involving football fans in France had dropped to six incidents so far this season, mainly in Paris, compared with 19 over the same period last year.
However, he admitted that after some trouble-makers were excluded from attending matches, "pre-planned" fights between rival fans were taking place outside the stadiums, for example in nearby car parks.
Mr Gaudin estimated that another 300 known hooligans could find themselves banned from matches, while the football league says that from now on, all football stadiums must install video surveillance cameras.
PSG is a club that is known to have a notoriously racist fan base. Black players often suffer racist chants or insults, while white gangs have been known to fight their black and Arab counterparts during or after games.
The Boulogne Boys group of supporters, with whom the dead fan Julien Quemener was linked, are said to have modelled themselves on British football hooligans in the 1980s, though the group says it is not linked to the far-right or political in any way.
The Paris Saint-Germain fan's death led to protests on the stands
The name comes from the Kop of Boulogne, or KOB for short, one of the two main stands PSG supporters occupy at the stadium - the "kop" a direct reference to Anfield in Liverpool.
The authorities have warned that some groups of supporters could find themselves being disbanded if there is further violence at PSG matches - with the possibility that future matches could be closed to the public if the French football association deemed it necessary.
About 300 PSG supporters held a silent march on Sunday in memory of the fan who was killed, carrying a banner reading: "Murdering authorities - truth for Julien."
The KOB website has put out a call for PSG fans who may have witnessed the shooting to report to the police in order to put 'their side of the story' to balance what they say is a one-sided account in the media.