UN judges will on Wednesday hand down a judgment in the last case before the tribunal in The Hague that has been prosecuting war crimes stemming from the bloody breakup of Yugoslavia in the Balkan wars of the 1990s.

They will issue a verdict – it is still subject to appeal - and sentences in the case of two former aides of the late Yugoslav president Slobodan Milosevic for their roles in the conflicts, in which 200,000 people died.

Jovica Stanisic, former head of Serbia's state security service, and his subordinate Franko "Frenki" Simatovic were handed over to the court in 2003 and acquitted in 2013.

But appeals judges ordered a retrial in 2015.

Prosecutors have asked for the maximum life sentence for Stanisic and Simatovic, who are now in their early 70s.

Both have pleaded "not guilty" to crimes including murder and persecution.

Prosecutors say the men helped to finance, train and equip Serb militias in Bosnia and Croatia that conducted brutal "ethnic cleansing" campaigns against non-Serbs, leaving thousands dead and driving 340,000 from their homes.

"These two men were critical in making sure the war was fought the way it was fought," said Iva Vukusic, a historian at Utrecht University specialising in former Yugoslav paramilitary units.

"They are the men behind the scenes, they are the ones responsible" for atrocities in Bosnia and Croatia, Munira Subasic, who lost her husband and son in the 1995 Srebrenica genocide, told Reuters outside the court building.

Bosnian Serb soldiers and paramilitaries killed 8,000 Muslim men and boys after they overran the UN-declared safe zone of Srebrenica.

Prosecutor Serge Brammertz told journalists last month that the case provided a "direct link to Belgrade and the Milosevic regime" from atrocities committed in Bosnia and Croatia.

Milosevic died in his cell in 2006 while on trial for genocide and crimes against humanity.