One of the world's most wanted men, Radovan Karadzic, was arrested at a police raid in Serbia late on Monday 13 years after he was first indicted by the United Nations War Crimes Tribunal.

The raid was conducted by the Serbian security forces and the war-time leader of the Bosnian Serbs has been taken to a judge with the War Crimes Court in Belgrade, an official statement said, quoted by the B92 news agency.

However, the location and time of Karadzic's arrest, as well as other details remain unknown. But unnamed sources said the former president of the Republic of Srpska was arrested in Belgrade.

Chief Hague Prosecutor Serge Brammertz, who was due to visit Belgrade on Tuesday but postponed his trip, welcomed the news of Karadzic's arrest.

"My colleagues in Belgrade have informed me about a successful action the outcome of which was the arrest of Radovan Karadzic," a statement from the Tribunal said.

"This is a very important day for the victims who have awaited this arrest for over a decade. This is also an important day for international justice, because it clearly shows that no one is above the law and that all fugitives will face justice sooner or later," the statement also reads.

At the same time the Tribunal claimed that another war crimes fugitive, Ratko Mladic, lives in Serbia and must be handed over.