Three Serbian men have been arrested for an attack which left a German LGBT activist with life-threatening injuries.

The unnamed 27-year-old – who was in Serbia attending an LGBT conference – was left in a critical condition in hospital after sustaining life-threatening head injuries and internal bleeding after the attack in downtown Belgrade on Saturday.

Jovanka Todorovic of conference organisers Labris, told Associated Press that the man – identified only as D.L – was attacked by a group of young men who attacked him with a glass ashtray while shouting: “We don’t want foreigners in Belgrade!”

Hundreds of LGBT activists took to the streets on Saturday carrying placards reading ‘Stop the Violence’ and ‘Your Policies, Our Blood’. A heavy police presence protected the demonstrators.

The attack takes place ahead of a planned Pride parade scheduled to take place in two weeks time. It will be the first march since authorities banned them in 2010 following clashes between police and ultra-nationalists that left more than 100 people injured, reports Deutsche Welle.

CCTV footage of the attack – which contains violence – has been released by police.