Assumedly anti-gay hooligans tear-gassed an International Day Against Homophobia and Transphobia (IDAHO) concert in Montenegro's capital, Podgorica, on May 17, according to the European Parliament's Intergroup on LGBT Rights.
The report said about half the audience dispersed and some people sought medical attention.
In response, pride organizers canceled the May 31 pride parade, which was to have been the nation's first.
"Today we saw firsthand the total lack of political will from national authorities to protect LGBT people and their supporters," said MEP Ulrike Lunacek, co-president of the Intergroup. "As Montenegro further progresses as a candidate to join the European Union, all its citizens must be protected and respected by authorities."
The vice-chair of the European Parliament's Delegation to South East Europe, Jelko Kacin, added: "It is deeply regrettable that the first gay pride parade in the country should be canceled due to authorities' failure to unequivocally support the parade. ... Today, Montenegro failed to demonstrate that it wants to progress towards EU accession equally fast in all areas. Respect, protection and promotion of minority rights are a quintessential part of our common European values."