Former Bosnian Serbian leader Radovan Karadzic on Wednesday slammed as "monstrous" a guilty verdict handed down by a UN war crimes tribunal in his first court appearance since being sentenced to 40 years in jail.

Addressing a special hearing at the court in The Hague, Karadzic again proclaimed his innocence of all charges, including genocide, arising from the 1990s Balkans wars.

He urged the court to free him to prepare for his appeal against last month's judgement, revealing he had packed his bags ahead of the March 24 verdict at the International Criminal Tribunal for former Yugoslavia expecting to be released.

But UN war crimes judges ruled that Karadzic, the most high-profile figure convicted over the wars that tore Yugoslavia apart, bore criminal responsibility for murder and persecution during the 1992-95 Bosnian conflict.

Judge O-Gon Kwon pronounced Karadzic guilty of genocide for the 1995 Srebrenica massacre and nine other charges including extermination, deportations and hostage-taking in a verdict issued more than two decades after he was first indicted.

"Instead of the only right decision of acquittal and allowing me to leave (for) home, I had already packed in the detention unit ... We now have a judgement, it's monstrous, just like the indictment itself is monstrous," Karadzic said.

"For eight years I have participated in the proceedings in an exemplary manner to make sure that I would not contribute to compromising this tribunal in any way whatsoever," Karadzic told a special hearing which he had called to discuss his "mental health" issues.

Almost 8,000 Muslim men and boys were murdered and their bodies dumped in mass graves in July 1995 at Srebrenica in eastern Bosnia, when Bosnian Serb forces brushed aside lightly armed UN Dutch peacekeepers protecting a UN safe area.

The slaughter, judged by two international courts as genocide, was the worst bloodshed on European soil since World War II.