Thousands of people have protested in Serbia's capital Belgrade against the arrest of ex-Bosnian Serb army chief Ratko Mladic.
They hailed Gen Mladic as a hero and said he should not be handed over the UN's war crimes tribunal in The Hague.
There were clashes with police as the demonstration ended.
Gen Mladic faces extradition to The Hague on charges of war crimes including the 1995 Srebrenica massacre of 7,500 Muslim men and boys.
His son, Darko Mladic, said earlier on Sunday that despite the tribunal's indictment, his father had told him he was not responsible for the killings, committed after his troops overran the city.
"He said that whatever was done in Srebrenica, he had nothing to do with it," he said after visiting Gen Mladic in detention at Serbia's war crimes court.
At least 7,000 supporters of Gen Mladic gathered in central Belgrade to hear speeches from nationalist politicians and decry Mr Mladic's arrest.
"Cooperation with The Hague tribunal represents treason," said Lidija Vukicevic of the Serbian Radical Party.
"This is a protest against the shameful arrest of the Serbian hero."
The demonstrators also denounced Serbia's pro-Western President Boris Tadic.
Gen Mladic's arrest is considered crucial to Serbia's bid to join the European Union.
He evaded capture for 16 years after the end of the Bosnian conflict - just one of the ethnic wars unleashed in the 1990s by the break up of Yugoslavia.
As the rally ended, the mood turned ugly, says the BBC's Mark Lowen in Belgrade.
Some of the demonstrators clashed with police, throwing stones and flares. About 100 people were arrested, a police official said.
Our correspondent says the scene in Republic Square is now calm after riot police in armoured vehicles were deployed to disperse the crowd.
About 3,000 people, many of them former Bosnian Serb soldiers, earlier held a separate protest against Gen Mladic's arrest in the Bosnian village of Kalinovik, where he was born.
Gen Mladic is due to lodge an appeal on Monday against being transferred to The Hague tribunal.
A Serbian court has declared Mr Mladic fit to be extradited but his lawyer, Milos Saljic, says his health has deteriorated.
"I can tell you that his health condition today is much worse than yesterday. It is worse psychologically," he told the Associated Press on Sunday.
Gen Mladic was seized in the village of Lazarevo, about 80km (50 miles) north of Belgrade.
Following the arrest of Radovan Karadzic in 2008, Gen Mladic had become the most prominent Bosnian war crimes suspect still at large.
He was indicted by the UN war crimes tribunal in The Hague in 1995 for genocide over the killings that July at Srebrenica - the worst single atrocity in Europe since World War II - and other alleged crimes.
Having lived freely in the Serbian capital, Belgrade, he disappeared after the arrest of former Yugoslav President Slobodan Milosevic in 2001.
President Tadic has said the arrest brought the country and the region closer to reconciliation, and opened the doors to European Union membership for Serbia.