BELGRADE, Serbia  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 en route to The Hague early Wednesday, according to the Serbian war crimes prosecutor.

A motorcade carrying Mr. Karadzic to the airport left hours after stone-hurling nationalists clashed with the police in central Belgrade at a rally to protest his arrest last week on war crimes charges, and his likely extradition to stand trial before an international war crimes tribunal in The Hague.

Mr. Karadzic was escorted by masked Serbian security officers and taken from the Belgrade war crimes court at roughly 3:45 a.m., according to the prosecutor, Vladimir Vukcevic. Soon after, his plane was in flight, and it landed in Rotterdam, not far from The Hague, about two hours later.

He is the highest-level politician from the former Yugoslavia to be transferred to the court since Slobodan Milosevic, the former Serbian president, who was arrested in 2001 and died in his cell there in 2006 while awaiting a verdict.