Anti-extremism campaigners in Germany have hit upon a novel idea to expose neo-Nazi supporters.

A group called Exit Deutschland, which is dedicated to helping people turn away from far-right ideology, set up a stall at a nationalist music festival in the German twon of Gera.

Posing as T-shirt sellers specialising in neo-Nazi merchandise, they handed out to 250 people at Saturday's festival, shirts branded with the words "hardcore rebels - national and free" and images of nationalist flags.

But when the T-shirts were washed, the slogans changed to reveal a new message.

The clean garment told wearers: "If your t-shirt can do it, you can do it too - we'll help you get away from right-wing extremism."

The phone number for Exit Deutschland also appeared.

Gordon Richter of Germany's far-right NPD party was one of the festival planners. He told Reuters: "It's kind of pathetic that anyone spent money for something like that."