International judges will on Tuesday begin hearing an appeal by Bosnian Serb military chief Ratko Mladic against his life sentence for genocide over the Srebrenica massacre and other war crimes.

The two-day hearing in The Hague was delayed several times after Mladic, 78, needed an operation to remove a benign polyp on his colon and then because of the coronavirus pandemic.

Mladic, dubbed the Butcher of Bosnia, was sentenced to life behind bars in 2017 for war crimes, crimes against humanity and genocide for his role in the bloody Balkans civil war in the 1990s.

This included genocide committed by his Bosnian Serb forces in the small eastern Bosnian town of Srebrenica in mid-1995, Europe's worst bloodshed since World War II, where some 8,000 Muslim men and boys were slaughtered.

The defence will speak first at the International Residual Mechanism for Criminal Tribunals -- which deals with cases left over from now defunct tribunals for the former Yugoslavia and Rwanda. The prosecution will follow.

Mladic will himself be allowed to speak for 10 minutes on Wednesday although it remained unclear if he would be either in court or appearing via video-link from his detention centre in the seaside suburb of Scheveningen.

Mladic had to be dragged out of the court in 2017 after an outburst in which he accused the judges of lying.

- 'Doesn't have the energy' -

Mladic's son Darko told AFP the former military chief had been unable to properly prepare for the appeal hearing because of his health.

"He doesn't have the energy needed for work of this kind and there are questions about how well his memory is working," Darko Mladic said.

"His lawyers haven't been able to visit him and so there hasn't been adequate communication... So in several aspects he hasn't been able to prepare."

Judges however last week rejected a fresh request by Mladic's defence team for a delay on health grounds.

About 100,000 people were killed and 2.2 million others displaced in the 1992-95 Bosnian war, which erupted as communal rivalries tore Yugoslavia apart after the fall of communism.

Mladic was the military face of a trio led on the political side by ex-Yugoslav president Slobodan Milosevic and former Bosnian Serb leader Radovan Karadzic.

Haunting footage showed Mladic assuring people in Srebrenica they would be safe as his troops brushed aside Dutch UN peacekeepers, even as those troops were gearing up for the massacre.

The former general was captured in 2011 after years on the run.

Milosevic died in his cell in The Hague in March 2006, suffering a heart attack before his trial had finished, while Karadzic is serving a life sentence for genocide in Srebrenica and other atrocities.

- 'Important event' -

Both the defence and prosecution have appealed against the 2017 verdict against Mladic, with prosecutors seeking to overturn Mladic's acquittal for genocide in several areas other than Srebrenica.

The "Mothers of Srebrenica", a group of women related to victims of the massacre who have for years protested outside court, will not attend the hearing for the first time, due to the COVID-19 pandemic.

"It's the first time we haven't been to such an important event at the tribunal in The Hague," Munira Subasic, president of the main Mothers of Srebrenica association, told AFP.

She said she hoped there would be no further delays to the legal proceedings against Mladic because the tribunal "must not lose motivation, and must carry out its mission".

"We hope Mladic will be found guilty for genocide in other towns as well, not just those in Srebrenica."