Long one of the most-wanted fugitives in the world, Radovan Karadzic, the Bosnian Serb leader blamed for inciting his followers to join him in a brutal ethnic war, was delivered Wednesday to a prison cell in The Hague for eventual trial by a United Nations war crimes tribunal.Karadzic, who was arrested in Serbia last week, was taken from the Belgrade war crimes court, escorted by masked Serbian security officers, according to the Serbian war crimes prosecutor, Vladimir Vukcevic. Karadzic’s plane landed in Rotterdam, not far from The Hague, about two hours later. He was then transferred by helicopter to the Scheveningen penitentiary in The Hague, where the United Nations has its own modern cellblock. He is the highest-level politician to be transferred to the court dealing with war crimes committed in the former Yugoslavia since Slobodan Milosevic, the former Serbian president, who was arrested in 2001 and died in his cell there in 2006 while awaiting a verdict. The indictment of Karadzic charges that as president of the Bosnian Serb republic in the early 1990s, he helped orchestrate a 43-month siege of the city of Sarajevo, devised a systematic campaign to kill or drive out tens of thousands of non-Serbs from Serbian towns and villages, set up concentration camps and was an engineer of the massacre of nearly 8,000 unarmed men and boys captured at the United Nations-protected enclave of Srebrenica, in Europe’s worst mass execution since World War II.To avoid too much commotion at the prison, Karadzic may be kept separate from the other inmates for a few days, a court official said. Ahead of his arrival, the cellblock had held 37 men, among them former foes, allies and even subordinates of the former Bosnian warlord. Before his transfer to The Hague, about 15,000 of his supporters, some bused in from across Serbia and Bosnia by the far-right Radical Party, gathered in Belgrade on Tuesday to protest the new government that arrested him on July 21.Loyalists wearing T-shirts emblazoned with Mr. Karadzic’s image waved Serbian flags and chanted “Long Live Radovan!” and “Uprising! Uprising!” About 100 ultranationalists wearing masks, who had separated from the group, burned flares, attacked traffic lights with clubs and hurled stones at storefront windows. The police responded with tear gas, and the Serbian news media said more than 45 people suffered minor injuries. “Karadzic is a hero because he defended Serb lives during the terrible wars of the 1990s,” said Elena Pavovski, 24, a supporter of the Radical Party, whose members sang patriotic songs next to a banner on Republic Square that threatened Serbia’s pro-Western president, Boris Tadic. “Everyone knows that the war crimes tribunal in The Hague was designed to try Serbs while the war criminals who killed Serbs are set free.”The rally was seen as a test of the new government, which is made up of Tadic’s Democrats and the Socialist Party of the former Serbian strongman, Milosevic, which controls the Interior Ministry and the police.Before the rally began, Tadic implored the protesters to remain peaceful. He was determined to avoid a repeat of demonstrations in February, when thousands of radicals rampaged through Belgrade to protest Kosovo’s declaration of independence, looting shops and setting part of the United States Embassy on fire.The embassy warned Americans to stay away from central Belgrade on Tuesday night, while the embassy itself was guarded by troops with machine guns.