Police sealed off downtown Belgrade on Sunday for Serbia’s first gay pride parade in four years, seen as a key test of the EU hopeful’s commitment to protecting minority rights.

The parade was banned the last three years after hardline nationalists attacked marchers and clashed with police at the first-ever event in 2010, leaving 150 people injured.

Following new threats by far-right groups ahead of Sunday’s Belgrade Pride, several thousand anti-riot police, special police units, armoured vehicles and water cannons were deployed across the capital.

Only accredited reporters, organisers and participants wearing special bracelets were allowed to enter a large section of central Belgrade that was closed off to traffic.`

Some 500 members of the ultra-nationalist Dveri group were involved in a stand-off with officers in riot gear late Saturday as they tried to march on parliament to protest the planned gay pride march.

Interior Minister Nebojsa Stefanovic urged calm ahead of the parade, warning that authorities could still stop the event if security was threatened.

The two-kilometre (mile-long) march, set to start at 1030 GMT outside the main government building, will pass by parliament before ending in front of Belgrade City Hall.

Organisers were optimistic that the parade would go ahead, saying it had been met with a warmer reception than in previous years.

“For the first time the institutions have publicly supported the organisation of the pride and media reports were more favourable for the LGBT community,” one of the organisers, Boban Stojanovic, told reporters on Saturday.

Planners, who expect a few hundred people to attend the event, have released few details in advance due to security concerns.