ICTY trial: Mladic refuses to answer Srebrenica questions
28 January 2014 Last updated at 10:40 GMT
Two of the most powerful figures from the 1990s war in Bosnia are appearing together in public for the first time since the end of the conflict.
Ex-Bosnian Serb leader Radovan Karadzic has called ex-deputy Ratko Mladic to give evidence at the UN Yugoslav war crimes tribunal in The Hague.
Both men deny the charges against them. Mr Karadzic faces 11, including genocide relating to the Srebrenica massacre in July 1995.
However, when Mr Karadzic began his questioning, Mr Mladic refused to answer, citing his poor health and fear of prejudicing his own case.