BERLIN, May 20 (UPI) -- A new generation of neo-Nazis has German security officials concerned: The black-clad mob is extremely violent and growing in numbers.

On May 1 the northern German port city of Hamburg experienced the worst violence it has seen in years. A group of neo-Nazis attacked police and far-left demonstrators; the mob erected road blocks, set cars on fire and hurled bottles and stones at police. The police later said there would have been fatalities if it wasn't for the water cannons and the riot gear with which the officers broke up the two groups. Nevertheless, dozens of people, including several police officers, were severely injured.

May 1 has always been a traditional day of protests in Germany, always dominated, however, by far-left violence. For the first time, the street clashes in Hamburg shed light on a group of neo-Nazis who are purposefully pursuing violence. They dress in black hooded sweaters and wear black sunglasses and hats, making them look almost like their far-left rivals. Calling themselves "Autonomous Nationalists," these young neo-Nazis don't believe in political work -- they believe in violence only.

"This group wants to be excessively violent," Hajo Funke, one of Germany's leading experts on far-right extremism, told United Press International in a telephone interview. "And the problem is that more young extremists are joining them, fueled also by activities like the one in Hamburg."

The estimated total manpower of the Autonomous Nationalists over the past year has doubled to 440.