Dutch police Wednesday launched an investigation into an incident at a UN war crimes court, after former Bosnian Croat Slobodan Praljak military leader apparently swallowed poison when his 20-year jail term was upheld.

"Courtroom one is now a crime scene," presiding judge Carmel Agius said, as the appeals hearing resumed following the drama. He gave no details of the morning's drama, only to say that Praljak was now absent from the courtroom and that on his instructions the "Dutch have already commenced an investigation."