HAVANA, 21 (AFP) - The tumble that Cuban leader Fidel Castro (news - web sites) took in front of television cameras has relaunched speculation about the fragility of a regime built around the 78-year-old president.

Castro, who has headed the communist government in Havana for more than 45 years, broke his left knee and right arm in the fall on Wednesday night as he walked down steps after giving a speech to a graduation ceremony.

"These are quite serious injuries for a man of 78, but it is also a reminder that the succession question is open," said a western diplomat.

"Mortality is no longer an abstract question at this age."

For the Cuban people, who regularly hear rumours about Castro's health, the fall was a new sign of weakness in their leader, who feinted while giving a speech in June 2001.

The state however gives away very little about Castro's true health.

But his reputation is of a tireless leader who works into the early hours of the morning and sleeps little. He swims and does gymnastics and loves basketball.

His friend, Gabriel Garcia Marquez, the Colombian writer, says that when Castro "is tired of talking, he rests by talking."

But power is completely focused on Castro, who runs the island's daily management and diplomacy with an iron hand, ordering the official response to hurricanes and the daily power cuts that have badly affected the population and economy.

"Revolutionaries do not retire," is a favoured phrase of the Cuban leader, who remains a divisive figure in the world: some consider him a champion of the Third World and the "anti-imperialist" struggle while others only see the world's longest serving communist leader, struggling on 15 years after the fall of the Berlin Wall in Europe.

And he is determined to carry on.

After his fall, Castro "said even if I have to get casts, I can continue my work."

A government statement which announced his injuries, said Castro "is fit to continue working on basic issues in close cooperation with the party leadership and the state."

His determination leaves little place for his younger brother, Raul, the official leader-in-waiting, to increase his influence.

The 74-year-old brother runs the influential ministry of the revolutionary armed forces, which takes an ever greater role in the economy after taking control this year of the tourism industry, a key earner of foreign currency.

While Fidel Castro is considered austere, his brother is considered more fun-loving, but the two were guerrillas together and Raul was at his brother's side when the communist government was formed in 1959.

Diplomats and other observers often raise doubts however about Raul Castro's capacity to maintain the president's legacy.

"He pales next to the charisma of Fidel," said one diplomat, who doubted the younger brother's ability to take over.

The government statement called on the island's 11 million people to remain calm. Another diplomat commented, however, that Castro's fall "is just another of the ups and downs but it is not a turning point."

Faced with hardships that have mounted over the past 15 years, with electricity regularly cut for several hours a day, the Cuban people are exasperated at their worsening conditions but also fearful of the vacuum that would be left by the death of Cuba's leader.

Castro's team of doctors say it will not come soon.

His chief physician, Eugenio Selman-Housein Abdo, said in May that Castro would live for another 60 years.

"He is heading for 140 (years) and I am not exaggerating because now with the scientific progress and the development of embryo stem cells, man will become immortal," said the doctor, who described Castro's health as "formidable."

Miami, capital of Cuban exiles, abuzz with news of Castro's fall

MIAMI, 21 (AFP) - Known as the capital of Cuban exiles, Miami was abuzz with news of President Fidel Castro (news - web sites)'s accident, with many Cuban-Americans bemoaning that the communist leader only fell on his face, and not from power.

In Miami's Little Havana neighborhood, several Cuban-Americans said they were disappointed the man whose regime they fled years ago had not died, and only broke an arm and a knee.

At the Versailles restaurant, a favored meeting spot for Cuban exiles, Castro's fall was the topic of the day.

"I'm happy he got a good fall," said Guillermo Novo, laughing. "I'm only sorry he did not get really badly hurt."

Another customer, Antonio de la Cova, said the entire Cuban nation, watching the incident on television must have thought, and hoped Castro had died.

One caller to a Spanish-language radio station expressed outrage that journalists had spoken of Castro's "fall" -- which he gave listeners for a few seconds the impression Cuba's communist government had collapsed.

"This shows just how anxious Cuban people are to see the end of this nightmare," said Ninoska Perez-Castellon, a radio-journalist who heads the Cuban Liberty Council, one of several Miami-based anti-Castro groups.

"For 40 years, this man has been doing what he wants," she told AFP.

Another exile leader, Jose Basulto, was critical of the importance fellow Cubans gave to the incident.

"Instead of the activism that should be there to trigger the political fall of Castro, people are wasting time with nonsense such as this," said Basulto, who heads the Brothers to the Rescue group.

Castro calls for calm after breaking knee, arm in fall

HAVANA, 20 (AFP) - President Fidel Castro, Cuba's leader for more than 45 years, broke his left knee and his right arm in a fall, and urged the Caribbean country's population of 11 million to stay calm, a government statement said.

"The medical exam confirmed what the Commander in Chief himself anticipated, that after his accidental fall at yesterday's ceremony there is a fracture in his left knee and a fissure in the upper part of the humerus of the right arm, which will be treated appropriately," it added.

It also underscored that Castro, 78, "is in a good general state of health and his spirits are excellent."

The president "is fit to continue working on basic issues in close cooperation with the Party Leadership and the State," it added.

Castro "asked to have thanked in his name all of those who expressed their concern and solidarity. And he appeals to them to maintain calm," it said.

Television cameras captured the entire incident late Wednesday when the communist leader stumbled as he was descending a flight of stairs and fell on his side following a speech before graduates of an art school in Santa Clara, a city 280 kilometers (175 miles) east of Havana.

But he quickly got up with the help of his bodyguards and, sitting on a chair, hastened to assure the audience he remained in control and full of enthusiasm.

"Please excuse me for having fallen," Castro smiled, who was clad in his trademark olive uniform.

"Just so no one speculates, I may have a fracture in my knee and maybe one in my arm," he continued. "But I remain in one piece."

The audience, which gasped as it watched him fall, responded with cheers and thunderous applause.

The Cuban government, still in Cold War mode because of hostile relations with the neighboring United States, normally treats the medical condition of its leader as a state secret.

Castro joked about seeing pictures of him on the floor in Thursday's international media and voiced confidence he would again make front page news all over the world.

But the president left the event before it had concluded and was driven away in a car.

Before his fall Wednesday, Castro had visited the mausoleum of former comrade Ernesto Che Guevara, who was killed in Bolivia in 1967 as he was trying to foment a revolutionary uprising.

Flanked by Elian Gonzalez, the boy at the center of a bitter custody dispute between the United States and Cuba, Castro laid a wreath on Guevara's tomb.

Castro, whose reign has spanned more than four decades of US economic embargo, a US-abetted invasion attempt and 10 US presidents, has defined the Cuba of the late 20th century by setting it brusquely apart from the decades of US dominance that followed the United States' 1898 victory in the Spanish-American war.

He became a statesman and an icon of international socialism, sending as many as 15,000 soldiers to help Soviet-backed troops in Angola in 1975, and dispatching forces to Ethiopia in 1977.

A driving force behind the Non-Aligned Movement, Castro has been an always energetic symbol to developing countries that a sovereign nation, however small, could boldly thumb its nose at US policy and appear to get away with it.

The Jesuit-educated lawyer, who came to power in 1959 at age 32, has been the perpetual thorn in the side of the United States, which was alarmed and embarrassed by Castro's establishment of a Cold War communist-bloc nation in the Americas, just 144 kilometers (90 miles) off its southeast flank.