One group cut short a concert in Belgrade by the archival left-punkers The Exploited, by tossing tear gas into the audience of 1000 or so at the Student Cultural Center (SKC). Another group came in to verbally threaten participants in a discussion panel on the "fascist threat" in Novi Sad. Police reacted uselessly in both instances.
Odd as it may seem, appearing publicly as "fascists" is probably as far as these marginal and confused young people can get in terms of associating their behavior with something that people recognize. The tolerance of decent folks is probably the best treatment they will ever receive as well. If real fascists were ever to come to power thanks to their efforts, their "shock troops" would probably be among their earliest victims, as in the Night of the Long Knives.
Update: See the comments for the full text of the statement from the Independent Association of Journalists of Vojvodina (NDNV).
Update 2, 11 November: It looks like the police in Novi Sad are beginning to arrest members of the neo-Nazi group "Nacionalni stroj" after all. But they also want to file charges against the organisers of the meeting that was attacked for failing to file notice of a public meeting. Balance or something, what? But then the balance is upset again -- somebody is smashing the windows on shops owned by Chinese businesspeople in Valjevo.