Radovan Karadzic extradited to The Hague

Many protesters carried banners and wore badges with Karadzic's name and picture. Some chanted slogans against President Boris Tadic and called for his death.

"Thank you for showing that Serbia is not dead, although it is being killed by Boris Tadic," said Aleksandar Vucic, leader of the Serbian Radical Party, which organized the rally. "Thieves and bandits are ruling Serbia."

"We will fight for Serbia and Serbia will be free," he added, setting off thunderous applause and chants of "Uprising! Uprising!"

Still, police estimated the turnout at only 15,000 people — far fewer than expected. The last major nationalist rally, in February after Kosovo's declaration of independence, drew 150,000 people and led to an attack on the U.S. Embassy amid a violent looting spree.

Tuesday's protest was seen a test for Tadic's government, which is much more pro-Western than its predecessor. The president warned the right-wing extremists to remain peaceful.

"Everyone has the right to demonstrate, but they should know that law and order will be respected," Tadic said.