UN judges were forced to temporarily suspend a court hearing after a war crimes suspect "took poison" when his 20-year sentence was upheld.

Moments after his conviction appeal was rejected, former Croatian army chief Slobodan Praljak appeared to drink from a small bottle and yelled "I am not a war criminal, I oppose this conviction".

Praljak's lawyer said the 72-year-old "had taken poison" and presiding judge Carmel Agius called for a doctor and halted the proceedings at The Hague.

An ambulance arrived and paramedics were seen entering the courtroom. A guard at the court confirmed Praljak was alive and receiving treatment.

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Image: Praljak was convicted over a campaign to create an ethnically pure Croat ministate

Croatian state TV reported President Kolinda Grabar Kitarovic cut short an official visit to Iceland and the government was holding an emergency meeting.

Praljak was convicted of involvement in a campaign to drive Muslims out of Bosnia and create an ethnically pure Croat state during the Bosnian war in the 1990s sparked by the breakup of Yugoslavia.

The conflict mainly saw Bosnian Muslims fighting Bosnian Serbs, but there was also deadly clashes involving Bosnian Muslims and Croats after an alliance fell apart.

A total of 100,000 people died and 2.2 million were displaced in the three-year war.

'Evil Butcher of Bosnia' guilty of war crimes

Praljak was one of six political and military figures appealing against convictions at the International Criminal Tribunal for the former Yugoslavia (ICTY), which last week convicted former Bosnian Serb military chief Ratko Mladic of genocide.

The six includes former defence minister Jadranko Prlic, whose 25-year sentence for involvement in the campaign to create an ethnically pure state was upheld.

Croatia claims it has "clean hands" over the 1992-95 war in Bosnia and wanted the decision overturned.

Thousands died at the hands of Mladic

Zagreb has also expressed anger at the UN judges for upholding a finding that the late Croat president Franjo Tudman was part of a plan to create a ministate in Bosnia.

Tudjman's son, Miroslav, said Praljak's move was a "consequence of his moral position not to accept the verdict that has nothing to do with justice or reality".

The three other suspects - Milivoj Petkovic, 68, Valentin Coric, 61, and Berislav Pusic, 65 - have yet to learn their fate.

The court, established by the UN in 1993, is due to close when its mandate expires at the end of this year. It has indicted 161 suspects, of which 90 have been convicted.