Rolf Fera says he forgot he had registered the website address www.adolf-hitler.de until he started getting death threats five months ago. They came from extreme-right and extreme-left groups in Germany who each wanted the address for their own ends, he says.

"I would have given the address to an institute or a historian, but I'm not a well man so I got rid of it," he says. Not before he was hunted down by the German media and investigated for right-wing sympathies.

"It was a witch-hunt. I am not politically active and I don't know anything about neo-Nazis," says Mr Fera, He registered the site to prevent neo-Nazis using it, he says.

The fight for control of www.adolfhitler.de gives an indication of the new battleground in Germany's war against extremism: the Internet.

Germany's constitution explicitly bans racially-based hate propaganda, Holocaust denial and Nazi glorification. Yet the outpouring of neo-Nazi and other race-hate sentiment from Internet websites based outside Germany is now undermining these constitutional safeguards.

Last week, Germany's national laws came head to head with the transnational medium that is the Internet.

The Supreme Court ruled on Wednesday that German laws outlawing Holocaust denial and spreading right-wing extremist propaganda apply to all Internet websites accessible in Germany, regardless of where the website is based.

The ruling, which could have serious implications for freedom of expression on the Internet, was made in the case of Dr Frederick Toben, a German-born Australian citizen who maintains a website that discusses what is known in Germany as "the Auschwitz lie".

A German state court ruled last year that German law had no jurisdiction over a website based in Australia but the Supreme Court overturned that ruling. Dr Toben was not in court for the hearing and said he would ignore the court's ruling.

"Germany is trying to rule the world again by saying that the people who access the Internet have no choice. If someone is offended by the material, they can switch off," he said.

The controversial right-wing historian David Irving lost a libel action earlier this year against an author who accused him of being a Holocaust denier. He criticised the decision as an attempt by the German government and judiciary to use the law to discourage free speech.

"I for one don't intend to let the German government give me a lesson on freedom of speech. I think they could learn a thing or two about freedom of speech from their last 100 years or so," he says.

"I think the ruling reflects their frustration. They want control and thought they had everything laced up and yet this was growing under their feet like grass all the time," adds Irving.

Germany's deputy Interior Minister Brigitte Zypries says while the fight against German neo-Nazi websites will continue, it is unrealistic to try to shield Germans from foreign websites. "It is right to act against right-wing radicalism but it is wrong to create hysteria. We are not happy about this but that's life and that's the Internet and you can't change it. You can't build a wall around Germany," she said.

Dr Toben is unlikely to be prosecuted as it would require his extradition from Australia. However, the ruling could prove an important weapon for German prosecutors in their fight against extreme-right websites.

These sites are spreading fast and becoming increasingly aggressive, according to Germany's Office for the Protection of the Constitution or BfV in Cologne. This year the BfV has logged almost 400 German websites containing extreme-right views, up from only 32 websites four years ago. "Any idiot can create his own website these days," says Wolfgang Cremer of the BfV.

The Internet is bringing the traditionally fragmented extreme-right closer together, creating solidarity at a time when many organisations and events are banned.

Sites contain information about demonstrations, Nazi imagery and music downloads from bands such as White Aryan Resistance, as well as chat rooms full of expletives and explanation marks.

"In the current situation, terror is our only course of action. Destroy what is destroying you! Civil war will come," writes one anonymous chat room contributor.

Extreme-right groups take advantage of the Internet's decentralised structure and place content that might be punishable under German law on computer servers in the US.

Even with the Supreme Court ruling, it is unlikely German prosecutors will be able to secure prosecutions in the US where freedom of speech is guaranteed by the first constitutional amendment.

A comment posted in a chat room sums up the difficulties the German government faces in dealing with the growth of neo-Nazism on the Internet.

"The Internet was designed to survive a world war, so it will also survive German criminal law."