The Spanish news agency Efe quoted diplomatic sources as saying that the 62- year-old monarch had collapsed after a heart attack while on holiday with his Spanish-born wife, Fabiola. His body was to be flown home immediately.
King Baudouin succeeded to the Belgian throne in July 1951 on the abdication of his father, Leopold III, who was engulfed in a controversy over his conduct in the Second World War.
He had been in failing health for a year and last year underwent heart surgery, Efe reported.
The Belgian prime minister, Jean Luc Dehaene, has summoned a special cabinet meeting this morning.Reuse content