The Swiss authorities fear sporting events are becoming a recruiting ground for rightwing extremists.
They warn that contact between football hooligans and far-right groups has coincided with an upsurge in violence at stadiums.
“There has been an rise in the number of violent incidents in Swiss football and ice-hockey stadiums. More and more, rightwing extremist attitudes are spreading among hooligans,” said the Federal Police Office in a report on internal security.
“Rightwing groups are trying to use the tendency for violence at certain sports events for their own ends.”
Spokeswoman Danièle Bersier confirmed that there had been an increase in attacks by skinheads and hooligans on supporters and security forces.
The number of hooligans in Switzerland is estimated at between 200 and 300, according to Zurich City police.
Police say they have seen a slight increase in numbers, but admit that it is impossible to say how many hooligans belong to an extreme rightwing organisation.
Experts point out that there are clear differences between violent sports fans and rightwing extremists.
Hooligans are widely considered to be racist but non-political, while so-called skinheads are seen as acting for political motives.
Christoph Vögeli of Zurich City police said there were also hooligans, notably in Zurich, who explicitly distanced themselves from rightwing extremism.
Over the past few months police have documented a handful of incidents at Swiss sports stadiums involving an extremist rightwing element.
In February police arrested six alleged militants after an ice-hockey match between two teams from Bern and Fribourg. Hooligans in Lugano are also known to be members of far-right organisations.
In another incident around 20 young people shouted Nazi slogans during an ice-hockey match in Zurich. They were arrested and later released with a caution.
More than ten years ago self-styled neo-Nazi supporters regularly attended matches of Geneva’s leading football club, Servette. The group has apparently dissolved.
The recruiting phenomenon is well known in Britain. A neo-Nazi group, Combat 18, has used football matches to spread its political beliefs and draft new members.
Observers are concerned that extremists might cause trouble at the 2008 European football championships, jointly organised by Switzerland and neighbouring Austria.
Police say existing legislation against hooliganism is not sufficient to tackle the problem, but moves are underway to tighten the law.
A new law, currently being drafted, foresees travel bans for violent sports fans as well as preventive detention for known hooligans.
Guido Balmer, spokesman for the Federal Police Office, said detention would only be used as a last resort.
Officials have also called for closer international police cooperation ahead of Euro 2008.
The cabinet is due to appoint a special working group for the tournament, made up of representatives of the federal, cantonal and local authorities.
swissinfo with agencies
The 2003 report on Internal Security says violent incidents are on the rise in Swiss sports stadiums.
Police say sports events are being used by rightwing extremist groups to recruit new members among violent football and ice-hockey supporters.
The authorities hope to have a new law in place by 2008 to combat hooliganism.
The Federal Police Office estimates the number of rightwing extremists at about 1,000, with 700 fringe supporters.
The majority of extremists are believed to come from rural areas in German-speaking Switzerland.