Roving gangs have attacked gay rights activists holding their first march in Belgrade, circling them one by one and kicking them until police intervened.
Dozens of people have reportedly been injured, including a half dozen police officers deployed to the capital's main square.
Hospital officials say none of the injuries are life-threatening.
The gay pride event is just one of several marches being held throughout Europe this month to draw attention to discrimination against homosexuals and to urge political leaders to grant them equal rights.
Soccer hooligans and ultra-nationalists appear to be among the attackers.