Dozens of Croat war veterans have protested in the Croatian town of Vukovar against signs that were written in both the Latin and the Cyrillic alphabets.
The rally on September 3 comes a day after protesters in Vukovar clashed with police as they destroyed several signs in official buildings.
The Croatian and Serbian languages are similar, but Croats use the Latin alphabet while Serbs use Cyrillic.
The protesters want Vukovar to be exempted from a law stipulating the use of Cyrillic in areas where Serbs make up at least one-third of the population.
Vukovar was devastated by Serbian rebels during Croatia's war for independence in the 1990s.
The city has been rebuilt but ethnic tensions remain.
Ethnic Serbs make up some 4 percent of Croatia's population of 4.2 million.
Based on reporting by AFP, AP, Reuters, and RFE/RL's Balkan Service