Slobodan Milosevic's death months before a verdict in his war crimes trial was the result of heart failure, the U.N. said on Sunday, but more tests were needed to decide whether it was from natural causes or suicide.

A preliminary autopsy report on the body of Milosevic, branded the "Butcher of the Balkans" over the 1990s conflicts, presented the heart failure finding as some world figures and war victims' relatives said the death robbed them of justice.

The autopsy on the body of the 64-year-old former Yugoslav president, who had a heart condition and high blood pressure, was conducted by Dutch scientists and attended by Serbian pathologists. Serbia said the autopsy was very professional.

Milosevic, found dead in his cell on Saturday, faced a possible life sentence over the tribunal's charges on 66 counts of genocide, crimes against humanity and war crimes involving conflicts in Bosnia, Croatia and Kosovo as Yugoslavia imploded.

"According to the pathologist, Slobodan Milosevic's cause of death was a 'myocardial infarction' (heart failure)," said a statement issued by the U.N. war crimes tribunal in The Hague.

"A toxicological examination will still be carried out," it said. A tribunal spokeswoman said the final report on Milosevic's death may take more than a day.

The tribunal said Milosevic's body would be released to his family on Monday but it was not immediately clear where it would go -- his widow lives in Russia and faces arrest in Serbia -- and where the burial or cremation would take place.

Milosevic's lawyer Zdenko Tomanovic said his client had feared he was being poisoned, but the tribunal rejected a request for the autopsy to be done in Russia, close ally of the former Yugoslavia and home to Milosevic's wife, brother and son.

Tomanovic said his client had written to Russia asking for help a day before his death, adding he had been given the wrong drugs -- including some for leprosy -- in a bid to silence him.

Cardiologists treating Milosevic in The Hague had warned he was at risk of a life-threatening condition known as a hypertensive emergency, when surges in blood pressure can damage the heart, kidneys and central nervous system.

SUSPICIOUS TRACES

Reports emerged indicating Milosevic may have had suspicious traces in his blood or had not been taking medication.

A blood sample from Milosevic in January contained traces of drugs used to treat leprosy or tuberculosis that can neutralize medicine for high blood pressure and heart problems, Dutch public TV NOS reported, quoting an unnamed tribunal adviser.

Tribunal president Fausto Pocar said he had ordered a full inquiry and that Dutch authorities were also investigating.

Del Ponte told a news conference in The Hague that on behalf of Balkan war victims she regretted the death.

"It deprives the victims of the justice they need and deserve," she said. "Now more than ever I expect Serbia to finally arrest and transfer Ratko Mladic and Radovan Karadzic to the Hague as soon as possible."

Serbia is under pressure to send former Bosnian Serb leader Karadzic and his military commander Mladic -- like Milosevic both accused of genocide -- to The Hague or jeopardize its hopes of joining the European Union, up for discussion next month.

It was not clear whether Milosevic's widow Mira Markovic would come to The Hague to collect his body. She visited him at the detention center until 2003, when she fled Serbia for Russia to avoid arrest on charges of abusing her power.

Serbian President Boris Tadic said Milosevic should not get a state burial and he would not grant an amnesty to his widow.

Apart from a vigil by about 100 die-hard and mostly elderly supporters at Milosevic's old party office in Belgrade on Saturday, there was little display of grief in Serbia.

By contrast, hundreds in Belgrade placed wreaths on the grave of reformist President Zoran Djindjic, who ousted Milosevic and who was assassinated three years ago.

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