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 Aug. 13, said late on Monday in a statement read on Cuban television that he would be out for "some weeks" following the operation to stem intestinal bleeding.
The seriousness of Castro's condition was not clear, but news he had ceded power sparked hopeful celebrations among Cuban exiles in Miami who had been waiting decades for his demise.
The White House, where a succession of US presidents had plotted Castro's downfall, stayed low key but watchful.
"We are monitoring the situation. We don't want to speculate on his health," said Peter Watkins, a White House spokesman. "We will continue to work for the day of Cuba's freedom."
Thousands of people celebrated in Miami's Little Havana and in nearby Hialeah and Westchester, convinced of Castro's imminent demise.
The crowd banged pots and pans, honked car horns, waved flags and chanted "Viva Cuba Libre" -- "Long Live Free Cuba." Some tried to contact friends and relatives in Cuba by cellphone.
In Havana, Cuban dissident Marta Beatriz Roque said Castro's decision "took us by surprise."
"This needs to be followed very closely," she told Univision, a Spanish-language US broadcaster.
Castro has been a major world figure since his band of bearded guerrillas seized power from dictator Fulgencio Batista in January 1959. His rule has been marked by momentous events such as the Cuban missile crisis and the failed US-backed Bay of Pigs invasion in the 1960s.