The unusual legal definition follows an investigation into a 2010 mass brawl in the Chelyabinsk region town of Miass, where a group of baseball bat-wielding and gun-toting thugs swooped down on a rock festival, injuring 19 concertgoers.
Photos from the scene showed shirtless men beating up music fans. Punk band Tarakany (Cockroaches), which performed during the assault, fled the stage after being fired at.
Initial news reports said 80 attackers had acted on behalf of the owner of a local Armenian restaurant who had quarreled with music fans dining at his establishment.
But the local branch of the Investigative Committee said in a statement Tuesday that the attackers were an "organized group" intent on inciting hatred toward an "informal social group" — rock fans.
Investigators said 13 suspects have been charged with inciting hatred and mass rioting, punishable with five to 10 years in prison. Three additional suspects are on a federal wanted list, and a fourth is wanted internationally, they said.
Hate-mongering is a controversial criminal charge due to the absence of clear definitions of the legal terms "inciting hatred" and "social group." Investigators have used the charge of inciting hatred against dissenters of all stripes, including art curators Andrei Yerofeyev and Yury Samodurov, who organized an anti-religion exhibit in 2006, and several bloggers who criticized the police — whom investigators have ruled as a social group.