Dozens of protesters in the Croatian town of Vukovar have torn down signs written in the Serbian Cyrillic script.
The signs had been put up because of a law that makes bilingual signs mandatory in any area where more than one-third of the population belongs to an ethnic minority.
Vukovar was reduced to rubble during the war for independence with Serb-dominated Yugoslavia in the 1990s.
The town has now been rebuilt, but ethnic tensions remain.
The signs were put up on some of Vukovar's official buildings on Monday morning, but not long afterwards Croatian war veterans wielding hammers came to remove them.
"The protesters managed to overcome the police protection and smash new signs in Cyrillic on the local tax office and police station," the state news agency Hina reported.
"Cyrillic letters used to come to Vukovar on army tanks," one of the protesters, called Josic, told local media, referring to the occupation of the town by Serb rebels during the 1991-1995 war.
The Croatian and Serbian languages are linguistically similar, but Croats use Latin script while Serbs use Cyrillic.
Croatia became the European Union's 28th member in July.