ZAGREB, Nov 29 (Reuters) - The wartime commander of Bosnian Croat forces, Slobodan Praljak, died after he drank poison seconds after United Nations judges turned down his appeal against a 20-year sentence for war crimes against Bosnian Muslims, Croatian state television reported.

The broadcaster quoted sources close to Praljak as saying he had died in a hospital in The Hague on Wednesday.

Appeals judges at the U.N.'s Yugoslav war crimes tribunal upheld the convictions of six Bosnian Croats found guilty of war crimes and crimes against humanity during the 1990s, in the court's last verdict before it closes next month.

After the judge confirmed his sentence, Praljak, 72, took a swing from a glass and said: "I just drank poison." He also said: "I am not a war criminal. I oppose this conviction."

The presiding judge suspended the hearing and called for a doctor. An ambulance was at the building and paramedics went to the courtroom.

"Former head of the chief headquarters of the Croatian Defence Council, General Slobodan Praljak, died in a hospital in The Hague after he drank poison in a courtroom after the International Criminal Tribunal for the Former Yugoslavia confirmed his 20-year sentence for war crimes," Croatian TV said.