Former Bosnian Serb leader Radovan Karadzic did not enter a plea during his initial appearance at the UN war crimes tribunal in The Hague, Netherlands, on Thursday. (Jerry Lampen/Associated Press)

Former Bosnian Serb leader Radovan Karadzic made his first appearance Thursday before a war crimes tribunal in The Hague, saying he would represent himself in the proceedings.

"I have an invisible adviser, but I have decided to represent myself," the freshly shaven and visibly tired Karadzic told a judge at the International Criminal Tribunal for the former Yugoslavia.

When Judge Alphons Orie asked him if his family knew where he was being held, he replied: "I do not believe there is anyone who does not know that I am in the detention unit."

Karadzic, 63, stands accused of masterminding Europe's worst massacre since the Second World War, the killing in 1995 of some 8,000 Muslim men and boys in the town of Srebrenica.

Karadzic is charged with 11 counts of genocide, war crimes, crimes against humanity and other atrocities relating to the 1995 massacre and other acts against Muslim, Croat and other non-Serb civilians in Bosnia and Herzegovina during the 1992-95 war.

He wore a dark suit and tie for the hearing, and listened intently as Orie read a summary of the indictment outlining the charges.

Karadzic did not enter a plea, saying he first wanted to read a new indictment that prosecutors are preparing.

The judge indicated he was unaware of the new indictment, but said any amendment to the existing indictment would require the approval of the tribunal.

Prosecutors confirmed they were working on revisions, but added that the amended indictment would not necessarily include any new charges.

Orie told Karadzic if the prosecution has not finished its work within 30 days, he will be asked to enter a plea on charges contained in the existing indictment.

His next appearance before the tribunal has been scheduled for 2:15 p.m. on Aug. 29.

Karadzic's arrival in The Hague on Wednesday marked the end of a 13-year effort by the tribunal to get hold of its most wanted war crimes suspect.

Hardly recognizable with his thick white beard and long hair at the time of his arrest, the former poet had been living in hiding in Serbia for more than a decade, practising alternative medicine and writing columns for a local magazine under an assumed name.

Trial preparation to take months: prosecutor

Karadzic has said he doesn't recognize the tribunal. Relatives have told the media that he plans to reveal at his trial alleged promises made to him by the United States and France that he wouldn't be prosecuted if he ended the Bosnian war, the CBC's Mike Hornbrook reported Thursday.

Although the two countries strongly deny the allegations, some people cite them as the true reason Karadzic was able to avoid facing justice for so long.

Speaking to reporters, prosecutor Serge Brammertz conceded the case would not be easy, but said his team would draw on evidence already presented in other cases since Karadzic's original 1995 indictment. They are expected to update the indictment before the trial begins.

"We will ensure that it reflects the current case law, facts already established by the court and evidence collected over the past eight years," he said.

Brammertz said it will take months for both sides to prepare for the trial.

Former Serbian president Slobodan Milosovic also opted to defend himself before the war crimes tribunal on charges that included crimes against humanity and genocide.

During his four-year trial, Milosovic launched into diatribes and posed rambling, unfocused questions to witnesses, drawing frequent rebukes from the judges.

He died of a heart attack on March 11, 2006, in his prison cell at The Hague before a verdict was reached.

With files from the Associated Press