A wartime leader of Croatian Serbs has committed suicide at the U.N. War Crimes Tribunal prison in The Hague. Milan Babic was serving a 13-year prison sentence for crimes committed against non-Serbs in the early war years. 

Milan Babic (File photo)

Fifty-year-old Milan Babic was scheduled to be in court Monday, continuing his testimony against another former Croatian Serb leader, but tribunal officials say he was found dead in his cell at 6:30 local time Sunday evening on a routine half-hour security check.

Dutch authorities have ruled it a suicide, and the court's president has already ordered an internal inquiry into Babic's death.

Babic was president of the self-declared breakaway Krajina Serb republic, covering about one-third of Croatian territory, after Croatia declared independence from Yugoslavia in 1991. He was jailed in 2004 for crimes committed during Croatia's 1991-1995 war.

In return for his guilty plea, prosecutors dropped four other charges of murder, cruelty and the wanton destruction of villages.

Babic was transferred to serve his sentence abroad, after judges rejected an appeal against his lengthy sentence. He was brought back to The Hague last month to testify in the trial of Milan Martic, another Croatian Serb.

The ultimate insider witness, Babic also testified against former Yugoslav President Slobodan Milosevic in 2002. They were allies in the early war years.

A dentist by profession, Babic had expressed shame and remorse over his actions in Krajina. But tribunal officials say they had no indication that Babic was depressed. One tribunal observer, however, said Babic was solemn, quiet and only smiled once during his recent week of testimony.

Babic is the second person to commit suicide at The Hague prison. Croatian Serb Slavko Dokmanovic killed himself in 1998.