Bosnian Serb ex-Army Chief Ratko Mladic goes on trial on Wednesday, accused of war crimes and crimes against humanity in his campaign of ethnic cleansing and the massacre of Muslims at Srebrenica.

Prosecutors will open his long-awaited trial at 9:00 am (0700 GMT) before judges at the ex-Yugoslavia war crimes court in The Hague, just short of a year following his arrest in Serbia after 16 years on the run.

Mladic, now 70, has been indicted on 11 counts of genocide, war crimes and crimes against humanity for his role in the Balkan country's brutal 1992-95 war that killed 100,000 and left 2.2 million others homeless.

Former Bosnian Serb political leader Radovan Karadzic -- Mladic's political alter ego -- is already on trial before the International Criminal Tribunal for the former Yugoslavia. Both men are believed to be the main players in a plan to rid multi-ethnic Bosnia of Croats and Muslims.

Dubbed the "Butcher of Bosnia", Mladic is specifically accused over the tragedy at Srebrenica in July 1995, when almost 8,000 Muslim men and boys were systematically murdered as UN peacekeeping troops helplessly looked on.

Prosecutors also hold him responsible for the 44-month siege of Sarajevo where his forces waged a "terror campaign" of sniping and shelling that left 10,000 civilians dead.

It was in pursuit of a "Greater Serbia" that Mladic allegedly ordered his troops to "cleanse" Bosnian towns, driving out Croats, Muslims and other non-Serb residents.

After the war, Mladic continued his military career but went into hiding in 2000 after the government of then Serbian president Slobodan Milosevic fell.

An indicted war criminal, he was on the run until May 2011 when he was arrested at a relative's house in Lazarevo, northeastern Serbia and flown to a prison in The Hague a few days later.

Better known from media images as a blustery commander in military fatigues, last June a sickly and haggard-looking Mladic made his first court appearance, opening proceedings by saying: "I am general Ratko Mladic... I defended my country and my people."

Mladic proceeded by pleading not guilty to the charges against him.

Two days ahead of the trial, his lawyers filed a request for a six month adjournment of the hearing, saying they did not have enough time to prepare for the defence.

A decision on that request is still pending, court spokeswoman Nerma Jelacic told AFP, adding "the trial chamber will make a decision when it is ready."

Rights organisation Human Rights Watch however said the opening of Mladic's trial was a "salient reminder that justice catches up with those accused of atrocity crimes."

"Victims have waited nearly two decades to see Ratko Mladic in the dock," Param-Preet Singh at the group's international justice programme said.

During the dozen or so hearings to prepare him for trial, the ageing former general spoke about little else except for complaining about his health and asking presiding Dutch Judge Alphons Orie if he could wear his military uniform.

His lawyer Branko Lukic said Mladic suffered three strokes in 1996, 2008 and 2011 and was partly paralysed on his right side.

The tribunal's president Judge Theodor Meron on Tuesday denied a defence request to have Orie removed from the bench after Mladic's lawyers questioned his impartiality as he had previously sentenced several former subordinates of Mladic.

The trial is to continue on Thursday, before resuming on May 29. It could go on for three years before a judgment is handed down.

If found guilty, Mladic could face a life sentence.