Prime Minister Zoran Milanovic was asked "not to test and provoke" those who defended Vukovar in the 1991-95 war.
The rally was organised by the Committee for Defence of Croatian Vukovar, which estimated that about 20,000 people attended.
Committee chair Tomislav Josic said the committee yesterday filed a motion asking the Constitutional Court to assess the constitutionality of the law on national minorities' rights, and that it expected the government to give up enforcing it until the court passed its ruling.
In demands read out by Josic, the committee wants the government to see to the arrest and prosecution of war criminals, and parliament to hold a discussion on the enforcement of the constitutional law at issue.
Josic said the committee wanted state institutions to enforce the law on the residence of every resident of Vukovar, and the town council to stop amendments to the town statute that would enable bilingualism in Vukovar.
Mayor Zeljko Sabo was criticised for not attending the rally and asked to distance himself within two days from the demand to introduce bilingualism, otherwise the committee expected him to resign.
Josic said the committee also reproached the mayor for not pointing out the problems the introduction of the Serbian language and script would cause, adding that those who signed the enforcement of the constitutional law in Vukovar would be responsible for undermining the security situation in the town and the coexistence that has been built over 15 years.
A proclamation by the Committee for Defence of Croatian Vukovar was also read out, asking the state and legislative authority to "turn the wheel" which "is heading towards the destruction of everything that has been created so far." The state authorities were accused of the high unemployment and discontent among the people, and urged not to put themselves above the people.
Among the protesters, who had arrived from all over Croatia and carried Croatian flags and flags of wartime units, were retired Croatian generals and the president of the Croatian Party of Rights Dr. Ante Starcevic, Ruza Tomasic.
At the end of the rally, the protesters were invited to a protest against bilingualism in Vukovar to be held in Zagreb in April.
According to the police, the protest passed without incident.