Glavas had been transferred from his prison cell to the clinical hospital in Osijek after his health deteriorated as a result of a long hunger strike.
Glavas was admitted to the hospital with chest pain and problems relating to blood pressure. He was diagnosed with an acute coronary syndrome.
Glavas, an independent member of Parliament who had been on a hunger strike for nearly 80 days is charged, along with six other people, with committing war crimes against civilians in Osijek in 1991.