"He was on holiday with his wife and friends and he died after a fall," a spokesman for his Flemish Christian Democrat Party said today.
"Our country has lost an extraordinary statesman, a valued colleague. Condolences to his family," Prime Minister Elio di Rupo said in a tweeted message.
Dehaene was a lifelong promoter of the European Union, working with such figures as French president Valery Giscard d'Estaing to push through reforms and enlargement.
In 1994, he made a bid to head the European Commission, the EU's executive arm, but lost out in the face of opposition from Britain which distrusted his federal Europe leanings.
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After the war, Dehaene excelled as a political negotiator, gaining national prominence in the 1970s.
By 1992, he was prime minister, holding the post for nearly eight years through tireless efforts to keep various coalition governments together in a Belgium notoriously divided between its Flemish north and French south.
This was the time too of the Dutroux paedophile killings, which rocked Belgium to the foundations as the country learned the police had missed a string of clues and that the killer had been freed from jail after serving just three years of a 13-year sentence for the abduction and rape of five girls.