The Serbian Interior Ministry has banned the Europride parade planned for next Saturday in the Serbian capital Belgrade.
There is a high risk that the safety of the participants and other citizens cannot be guaranteed, the state news agency Tanjug reported, citing the ministry.
Further details were not disclosed.
Pride parades, in which participants demonstrate for the rights of homosexuals and other members of the LGBTIQ* community, have been held in Belgrade since 2014 without incident.
Almost a month ago, however, Serbia's powerful President Aleksandar Vucic declared that this year's Pride had to be canceled or postponed for security reasons.
Vucic justified this with the tense situation surrounding neighboring Kosovo, which used to belong to Serbia and has been independent since 2008.
Serbia does not recognize the independence of Kosovo, which is now almost exclusively inhabited by Albanians.
After road blockades by ethnic Serbs in northern Kosovo at the beginning of August, however, the situation calmed down again.
Europride coordinator Goran Miletic said Tuesday evening in Belgrade that the parade will take place despite the decision of the Interior Ministry.
The organizers would appeal against the decision.
If the complaint is not upheld, they will take legal action.
"Disappointment" in Brussels
The EU has criticized the cancellation of the parade on Tuesday evening.
One is "disappointed" that the Serbian Ministry of the Interior has banned the train through the city, said the spokesman for the European External Action Service, Peter Stano, on Tuesday in Brussels.
The parade is a public declaration of the will to "fight discrimination" and to promote equal rights for non-heterosexual people.
The Council of Europe Commissioner for Human Rights, Dunja Mijatovic, also expressed regret.
The fact that the event has been in limbo for weeks has "given room for hate rhetoric and more threats against LGBTI people".
She explicitly criticized religious leaders.
In south-eastern Europe, "there is still a lot to be done to combat discrimination and hatred against LGBTI people," says Mijatovic.
Belgrade is the first city in south-eastern Europe to host a “Europride”.
Several MEPs and European politicians are also expected to attend Europride.
US Secretary of State Antony Blinken asked the Serbian government to allow the parade at the end of the previous month.
The federal government's queer commissioner, Sven Lehmann, appealed to Serbia on Monday to allow the Europride parade to take place and to protect it accordingly.