News of the arrest of Radovan Karadzic led to scenes of celebration on the streets of the Bosnian capital, Sarajevo.
By contrast, in the Serbian capital, Belgrade, an angry crowd of Mr Karadzic's supporters gathered outside the special court where he was being held, chanting "Karadzic hero".
In Sarajevo, which endured a 44-month siege by Bosnian Serb forces in the early 1990s, cars streamed through the city honking their horns, crowds cheered and some people took to the streets waving Bosnian flags.
"This is the best thing that could ever happen, you see people celebrating everywhere. I called and woke up my whole family," said Sarajevo resident Fadil Bico.
Disbelief at news
"I still cannot believe it," said Zijah Sehic, 18, who had been celebrating in the streets of the city. "I can't wait to see him in the tribunal in a few days."
Despite heavy rain, some young men dropped to their knees, slammed their hands against the ground and chanted "This is Bosnia!", correspondents reported.
I can't wait to see him in the tribunal in a few days
Edin Hadyiahmetovic, who was a soldier for the Bosnian army during the war, told the BBC News website that everybody around him was overjoyed to hear of the arrest.
"It is a great thing for us. Karadzic is a war criminal in everybody's eyes. We hope that he will get 30 years in jail," he said.
"Serving for almost four years in the Bosnian army, I have so many bad memories. My life in Sarajevo at that time was intolerable with no food, power and water. Nobody can imagine how bad it was."
In the northern Bosnian town of Kozarac, the organiser of a rock concert interrupted the show to announce the news, only to receive laughter from the audience and thumbs up for a good joke.
Zinaida Mahmuljin, who was in the audience, said it was only when mobile phones began ringing in the crowd and the news began to circulate that people realised the announcement was true. Then the party really started, she told AP news agency.
Meanwhile, there was little reaction to the news in Republika Srpska, the Serbian entity of Bosnia-Hercegovina.
No official comments were made and the streets were reported to be deserted.
Regional television showed a reporter stopping taxi drivers in the northern city of Banja Luka and asking their reaction to Mr Karadzic's arrest, AP said. Most had no comment, but one called it "a tragedy".
Protesters clash with police in the Serbian capital Belgrade
For some Serbs, Mr Karadzic remains a hero who stood up to ancient enemies and tried to create a separate Serb homeland.
Early on Tuesday, dozens of people, reported to be ultra-nationalists, gathered in front of the war crimes court in Belgrade to protest against Mr Karadzic's arrest.
They chanted "Karadzic hero!" and "Tadic Traitor!", in reference to Serbian President Boris Tadic.
Serbian television station B92 said that the demonstrators were outnumbered by police four to one.
Several people were reported to have been arrested after a confrontation with reporters in front of the courthouse.
Goran Pavelovich, who lives in the town of Kragujevac in Serbia, told the BBC News website of his surprise when he heard that Karadzic had been arrested.
"People didn't expect him to be arrested like this. Everybody here has quite mixed feelings," he said.
"Some are happy, some are very upset, some don't know what to think. People are really going to be talking about it. We always talk about politics and this is going to be the only subject of conversation at the coffee houses."
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