Bosnian Croat former military leader Slobodan Praljak died on Wednesday in a hospital after "drinking a liquid" during his appeal judgement by UN war crimes judges, a spokesman for the tribunal said.

"One of the six defendants... passed away today in the HMC hospital in The Hague," said court spokesman Nenad Golcevski. Immediately after sentence was passed on Praljak "he drank a liquid while in court and quickly fell ill," he added.

Efforts were made to give him medical treatment and he was "transported to the hospital where he passed," Golcevski said.