French hooligans' World Cup warning

The head of the police public order division, Pierre Mure, put the operation into chilling perspective. "It's an unprecedented operation for a sporting event," he said. "But there is no such thing as zero risk."

Despite the heavy police presence, skirmishes, some of them brutal, started before the match got under way with police, on foot and on horseback, moving in to disperse rival gangs.

Some 2,300 riot police, split into 18 units, patrolled the giant stadium, north of Paris, with a further 2,000 officers deployed to monitor transport routes and keep watch on potential trouble spots around the city. Several hundred undercover police were also working in the stadium, bringing the combined total close to 5,000 officers.

Jacques Chirac, the football-loving French president, was scheduled to attend the match, while the Interior Minister, Nicolas Sarkozy, who is in charge of the police, visited the Stade de France before the game to meet with riot police and other units.

Fears concerning the World Cup have been based on clashes involving right-wing groups based in the east of Europe. But here the trigger was plain, old-fashioned hatred between fans of two clubs.

Followers of PSG and Marseille fans have been involved in numerous clashes over the years. However, police also had to keep an eye on rival PSG supporters, since an added complication this time was the fierce rivalry between groups of PSG fans.

PSG won the argument on the pitch 2-1.