Antigay protesters disrupted a gay pride march Saturday in the Croatian coastal city of Split, throwing rocks, bottles, and firecrackers at the participants, the Associated Press reports.
There were about 200 marchers but thousands of opponents at the event. Several people were injured, and at least 100 were detained by police.
March organizers and supporters accused the police of not doing enough to prevent violence. "The state institutions did not do their job properly," said activist Sanja Juras.
Human rights group Amnesty International called for an immediate investigation. "The Croatian authorities need to act to stop this happening in future," said Nicola Duckworth, the group's director for Europe and Central Asia.
Croatian leaders, meanwhile, condemned the antigay violence. It has "shown that there are some non-European parts of our society," said President Ivo Josipovic. Prime Minister Jadranka Kosor said such attacks were "something that cannot be tolerated in Croatia."
The incident came a day after Croatia was accepted for membership in the European Union. A pledge to protect human rights was one of the conditions of its membership, which is scheduled to take effect in 2013.