Cuban President Fidel Castro, Latin America's sole surviving Communist strongman, ceded power to his brother Raul on a temporary basis for the first time in 47 years after undergoing what he called delicate intestinal surgery.
The aging but still-fiery leftist leader, who turns 80 on August 13, said in a statement read on Cuban television on Monday that he would be out for "some weeks" following the operation to stem intestinal bleeding.
The seriousness of Castro's condition was not immediately clear but news he had relinquished power sparked hopeful celebrations among Cuban exiles in Miami who had been waiting decades for his demise.
Castro's rule: Key dates
Jan 1959: Appointed prime minister in February.
The White House, where a succession of US presidents had plotted Castro's downfall, stayed low key but watchful.
In Havana, Cuban dissident Marta Beatriz Roque said Castro's announcement "took us by surprise."
Castro's 75-year-old brother and Defence Minister, Raul Castro, was temporarily handed the reins of the communist regime.
Raul Castro is already Castro's designated successor.
Castro blamed his ailment on the intense agenda of recent trips to Argentina and eastern Cuba.
"Working day and night and barely sleeping has taken its toll on my health, which has withstood everything, has undergone extreme stress and has become brittle," he said in a statement read over radio and television by his personal secretary Carlos Valenciaga.
"That touched off an acute intestinal distress with sustained bleeding, which forced me to undergo delicate surgery," he said.
The operations will "force me to forgo my responsibilities and duties for a few weeks.