Haider played an important part in the Austrian and European political life. He was the governor of the province of Carinthia and leader of the far-right Alliance for the Future of Austria.
"For us, it's like the end of the world," Haider's spokesman, Stefan Petzner, told the Austria Press Agency.
Haider, known for his charisma and intelligence, enjoyed tremendous popularity in Carinthia.
He had a wife and two daughters. The political life will feel a big change now, after his death.
