Lawyers for former Bosnian Serb military chief Ratko Mladic urged a UN court Tuesday to overturn his genocide conviction, saying the charges against him were "made out of thin air".

Mladic, now 78, was in particular "not tied" to any of the deaths in the notorious Srebrenica massacre in Bosnia in 1995, his defence team told the appeal hearing in The Hague.

His lawyers also argued that Mladic was at risk of a "miscarriage of justice" because he was mentally unfit for the two-day hearing against his 2017 conviction and life sentence over the wars that tore apart Yugoslavia in the 1990s.

Mladic was found guilty of genocide over the Srebrenica massacre, in which some 8,000 Muslim men and boys were killed, and for crimes against humanity and war crimes over the 1992-95 Bosnian war.

Bosnian Serb military chief Ratko Mladic -- dubbed the Butcher of Bosnia -- was sentenced to life behind bars in 2017 for war crimes, crimes against humanity and genocide during the Balkans civil war in the 1990s
Bosnian Serb military chief Ratko Mladic -- dubbed the Butcher of Bosnia -- was sentenced to life behind bars in 2017 for war crimes, crimes against humanity and genocide during the Balkans civil war in the 1990s AFP / PASCAL GUYOT

The once-feared general dubbed the "Butcher of Bosnia" appeared in court looking frail. He initially wore a surgical mask because of coronavirus restrictions but later removed it.

"I submit that the charge of genocide was made out of thin air," defence lawyer Dragan Ivetic told UN's International Residual Mechanism for Criminal Tribunals -- which handles cases left over from the Yugoslav tribunal that convicted Mladic.

"Any killings that happened outside of combat in Srebrenica were reprehensible but they were not tied to Mr Mladic."

Seeking a full acquittal, Ivetic said judges at the original trial "failed to establish the number of victims and their relation to any crime, let alone genocide".

Bosnian Serb military chief Ratko Mladic -- dubbed the Butcher of Bosnia -- was sentenced to life behind bars in 2017 for war crimes, crimes against humanity and genocide during the Balkans civil war in the 1990s
Bosnian Serb military chief Ratko Mladic -- dubbed the Butcher of Bosnia -- was sentenced to life behind bars in 2017 for war crimes, crimes against humanity and genocide during the Balkans civil war in the 1990s AFP / PASCAL GUYOT

But prosecution lawyer Laurel Baig urged judges to throw out Mladic's appeal. He had been "properly convicted and sentenced after a fair trial for some of the most heinous crimes of the 20th century", he said.

"Ratko Mladic is not a war hero, he is a war criminal. He abused his vast military power to deliberately target the civilian population, destroying lives, families and communities," Baig said.

Mladic was part of a Bosnian Serb leadership that caused "mass suffering in the name of ethnic ideology" as they tried to clear Bosnian Muslims and Croats out of huge swathes of the country, she added.

Bosnian Serb military chief  Ratko Mladic arrived in court wearing a mask because of coronavirus
Bosnian Serb military chief Ratko Mladic arrived in court wearing a mask because of coronavirus ANP / "UN-IRMCT/Leslie Hondebrink-Hermer"

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

Mladic was captured in 2011 after years on the run, and convicted following a three-year trial.

The prosecution are also appealing, seeking to overturn Mladic's acquittal on wider genocide charges.

Mladic will himself be allowed to speak for 10 minutes on Wednesday. He had to be dragged out of the court in 2017 after an outburst in which he accused the judges of lying about his health.

He briefly addressed the court on Tuesday to complain that the one-hour breaks between sessions -- needed to clean the court for coronavirus measures -- were too long for him to spend waiting in a small isolation room.

The hearing had already been delayed several times since March after Mladic needed an operation to remove a benign polyp on his colon, and then because of the COVID-19 pandemic.

Mladic's lawyers said they were taking part under protest on Tuesday after judges earlier this week rejected a bid to postpone it pending a fresh medical assessment.

"This hearing today is inappropriate and threatens... a miscarriage of justice," Ivetic told the court.

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.

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

The "Mothers of Srebrenica", a group of women related to victims of the massacre who have for years protested outside court, did not attend Tuesday's hearing for the first time, due to the pandemic.

"We hope Mladic will be found guilty for genocide in other towns as well, not just those in Srebrenica," Munira Subasic, president of the main Mothers of Srebrenica association, told AFP.