Updated 4.20pm

A wartime commander of Bosnian Croat forces died on Wednesday after drinking poison seconds after UN appeals judges upheld his 20-year sentence for war crimes against Bosnian Muslims.

Slobodan Praljak, 72, tilted back his head and took a swing from a flask or glass as the judge read out the verdict.

"I just drank poison," he said. "I am not a war criminal. I oppose this conviction."

The presiding judge, Malta's Carmel Agius, suspended the hearing and called for a doctor. The court said it would resume reading the verdict, which is also handling cases against five other defendants, including Milivoje Petkovic.

Praljak sat back down and slumped in his chair, a lawyer who was in the courtroom at the time said. He was taken to hospital by ambulance where he later died. 

"I just drank poison. I am not a war criminal. I oppose this conviction."- Slobodan Praljak

The dramatic events came in the final minutes of the court's last verdict before closing down. The International Criminal Tribunal for the former Yugoslavia (ICTY), established by the United Nations in 1993, shuts its doors next month when its mandate expires.

The court's lead suspect, former Yugoslav President Slobodan Milosevic, died of a heart attack in March 2006 months before a ruling in his genocide case.

Two defendants awaiting trial committed suicide by hanging themselves in their UN cells, according to court documents. Slavko Dogmanovic died in 1998 and Milan Babić was found dead in his locked cell in 2006.