Serbia's first openly gay prime minister Ana Brnabic is expected to attend a gay pride march in Belgrade, as police cordoned off the city centre with metal fences to secure the event.
Hundreds of police were deployed to control crowds in the downtown area of the capital ahead of the march and helicopters flew overhead.
Serbia's gays have faced widespread harassment and violence from extremists. More than 100 people were injured during a gay pride event in 2010 when police clashed with right-wing groups and soccer hooligans.
Ms Brnabic was elected this year in what was seen as part of Serbia's efforts to embrace change and improve its image as it moves toward European Union membership.