A United Nations war crimes court has been suspended after one of the accused apparently drank poison during an appeal hearing.

Slobodan Praljak, 72, a former commander of Bosnian Croat forces in Bosnia's between 1992 and 1995, shouted out "I am not a war criminal" and drank from a bottle moments after the judges at the international criminal tribunal for the former Yugoslavia (ICTY) confirmed his 20-year sentence.

The hearing at the purposely built court was suspended after Praljak's lawyer shouted "my client says he has taken poison".

One of the judges asked for the curtains to be brought down in the court during the ensuing panic.

Praljak was one of six former Bosnian Croat political and military leaders appearing in court connection with the Bosnian war.

The men were attempting to appeal against their convictions for involvement in crimes as Croat forces attempted to drive out Muslims from towns and villages during the 1992-95 war

Praljak is charged with ordering the destruction of Mostar's 16th-century bridge in November 1993, which judges said "caused disproportionate damage to the Muslim civilian population".

Slobodan Praljak
A wartime commander of Bosnian Croat forces, Slobodan Praljak, is seen during a hearing at the UN war crimes tribunal in the Hague Reuters/ICTY

The tribunal recently sentenced Ratko Mladic, the former Bosnian Serb general, to life in jail after being found guilty of war crimes an genocide in connection with the massacre of 8,000 Muslim men and children in Srebrenica as well as the three-year siege of Sarajevo in which 11,000 civilians died from shelling and sniper fire.

The hearing involving Praljak was the final case to be completed at the ICTY before it closes its doors in January having been established by the UN in 1993.

Slobodan Praljak
Croatian former general Slobodan Praljak stands prior to the start of his appeal judgement at the International Criminal Tribunal for the former Yugoslavia Getty