Protesters throwing stones and bottles clashed with baton-wielding riot police in Belgrade after several thousand Serbian nationalist supporters of jailed war crimes suspect Ratko Mladic rallied outside the parliament building to demand his release.
By the time the crowds broke up by last night, about 100 people were arrested and 16 minor injuries were reported.
That amounted to a victory for the pro-Western government, which arrested Mladic on Thursday, risking the wrath of the nationalist old guard in a country with a history of much larger and more virulent protests.
Rioters overturned rubbish containers, broke traffic lights and let off firecrackers as they rampaged through the city centre. Cordons of riot police blocked their advances, and skirmishes took place in several locations.
Doctors said six police officers were among the 16 people brought to hospital with minor injuries. Police remained on the streets as the crowds broke up.
The clashes began after a rally that drew at least 7,000 demonstrators, many singing nationalist songs and carrying banners honouring Mladic, 69, the former Bosnian Serb military commander. Some chanted right-wing slogans and a few gave Nazi salutes.
Supporters of the extreme nationalist Serbian Radical Party were bussed in to attend the rally. Right-wing extremists and hooligan groups also urged followers to appear in large numbers, creating the biggest test of Serbian sentiment and the government's resolve since Mladic's arrest.
The demonstrators, who consider Mladic a hero, said Serbia should not hand him over to the United Nations war crimes court in The Hague, Netherlands.
"Co-operation with The Hague tribunal represents treason," Radical Party official Lidija Vukicevic told the crowd. "This is a protest against the shameful arrest of the Serbian hero."
Demonstrators demanded the ousting of Serbian president Boris Tadic, who ordered Mladic's arrest. A sign on the stage read "Tadic is not Serbia".
More than 3,000 riot police were deployed around government buildings and Western embassies, fearing that the demonstration could turn violent and riot police tried to block small groups of extremists from reaching the rally.
Nationalists are furious that the Serbian government apprehended Mladic after nearly 16 years on the run. The former general was caught at a relative's home in a northern Serbian village.
The UN tribunal charged Mladic with genocide in 1995, accusing him of orchestrating the massacre of 8,000 Muslim men and boys in Srebrenica and other war crimes of Bosnia's 1992-95 war. Mladic's arrest is considered critical to Serbia's efforts to join the European Union, and to reconciliation in the region after a series of ethnic wars of the 1990s.
Mladic's son Darko said yesterday that despite the indictment, his father insists he was not responsible for the mass executions committed by his troops after they overran the eastern Bosnian enclave of Srebrenica in July 1995.
"Whatever was done behind his back, he has nothing to do with that," Darko Mladic said.
Mladic's family and lawyers have been fighting his extradition, arguing that he is too ill to face charges. The family plans to appeal against the extradition today and to demand an independent medical check-up.