The annual neo-Nazi skinhead rock concert known as Hammerfest will be held this Saturday in or near Boise, Idaho, where authorities say they are worried about the potential for violence at or after the event. Hammerskin Nation, one of the largest and most-dangerous neo-Nazi skinhead groups in the United States, is sponsoring the 25th annual gathering after patching up differences with a former rival, the equally violent Vinlanders Social Club. Both skinhead groups appear to be strengthening ties with so-called outlaw motorcycle clubs – bikers who say they are part of the “1 percent” crowd and pride themselves on a toughness that borders or crosses into criminality — according to information developed by the Southern Poverty Law Center. “We expect to see bikers at this year’s event,” said Mark Potok, senior fellow at the SPLC. Potok also said that the location of the event reflected new strength in the region. “The fact that it’s planned for Boise suggests that Hammerskin Nation is growing stronger in the Pacific Northwest than it has been for years,” he said. The exact location of this year’s Hammerfest hasn’t been announced and its promoters aren’t talking. Promoters are expected to use social networking sites and word of mouth to identify to location just hours before the event begins. Jeff Basterrechea, of the Boise Police Department’s gang unit, told the Idaho Statesman that groups like Hammerskin Nation typically don’t announce the location in advance “because they believe other groups will sabotage them,” the newspaper reported. “They’re so controversial, they’ll wait until the last moment to advertise where the concert will be,” he said. Often, militant anti-racist groups attempt to seek out white power music venues in order to prevent the bands from playing. Occasionally, violence has broken out between the so-called anti-fascists and the neo-Nazi rock enthusiasts.