Over 30 people were injured and 58 were taken into custody by Croatian police, after a clash with about 15,000 anti-government protesters who rallied in the capital city of Zagreb, media reports said.
Citing Croatian news agency HINA, Xinhua reported that the protesters, among whom were masked members of the Bad Blue Boys group of football supporters, demanded protection of war veterans from prosecution. They clashed with the police in an attempt to reach St Mark's Square, where the government is located.
Police used force as some protesters acted violently and tried to break the police cordon, Zagreb police chief Tomislav Buterin said at a news conference.
The injured in the process also include journalists.
Helicopters were also seen flying over the city.
At another Zagreb square, Bana Jelacica, thousands of people protested peacefully against the government and in support of a Croat war veteran awaiting extradition to Serbia in a Bosnian prison.
A similar protest was also organised in the eastern Croatian city of Osijek.
Croatian Prime Minister Jadranka Kosor called for the end to the protests, warning that instability could undermine Croatia's efforts to join the European Union.