Slobodan Praljak stood up and raised his hand to his mouth, tipped his head back and appeared to swallow a glass of something which, his lawyer told the court, was poison.
Slobodan Praljak was one of six former Bosnian Croat political and military leaders up before the court.
He was sentenced to 20 years’ imprisonment in 2013 for crimes in East Mostar.
He appealed the sentence but when he heard that his sentence had been upheld he told the judge “I have taken poison.”
According to the BBC Praljak stood up and raised his hand to his mouth, tipped his head back and appeared to swallow a glass of something which, his lawyer told the court, was poison.
The judge immediately ordered proceedings to be suspended and also asked that the curtains be lowered.
Before the curtains were brought down there seemed to be some confusion in the courtroom.
The judge called for the glass Praljak had drunk from to be kept. Someone else was heard saying that an ambulance had been called.