Cuban President Fidel Castro (search) tripped on a step and tumbled to the ground after leaving the stage at a graduation ceremony, fracturing a knee and arm but quickly returning to say that he was "all in one piece."

Castro's fall after a Wednesday night speech in the central city of Santa Clara was certain to launch a new round of speculation about the 78-year-old communist leader's health and the eventual succession after his 45 years of rule.

Castro's designated successor has long been his younger brother, 73-year-old Defense Minister Raul Castro (search), who fought with him in the Cuban revolution that overthrew President Fulgencio Batista (search) on Jan. 1, 1959.

A medical examination early Thursday confirmed that Castro suffered a broken left knee and a hairline fracture in his upper right arm, said an official notice read early Thursday on state television. Castro asked that the note be made public, the statement said.

Exclusive Associated Press Television News footage of the incident showed Castro tripping on a concrete step after he finished walking down the stairs from the stage. He fell onto the ground on his right side into the first line of chairs, banging his knee, hip, elbow and arm on the way down, as spectators looked on in surprise.

He was immediately surrounded by scores of security agents and others who rushed to help him up.

Castro's speech before the graduation ceremony for arts instructors was broadcast live on state-run television, but viewers could not see his fall. All that was visible was several of his security men running off to the side, evidently to assist him.

Less than a minute later, Castro appeared live on state TV, sitting in a folding chair and sweating profusely in his olive green uniform, and explained what happened to viewers across the island of 11.2 million people.

He said he felt like he had broken his knee and perhaps his arm — "but I am all in one piece."

"I will do what is possible to recover as fast as possible, but as you can see I can still talk," he said. "Even if they put me in a cast, I can continue in my work."

The note aired Thursday morning said Castro expressed thanks "for the innumerable expressions of concern and solidarity from the people."

"His general health is good, and is in excellent spirits," the note said. "He asked for calm, considering that very soon he will be back in place."

Castro was earlier seen leaving Santa Clara, about a three-hour drive east of Havana, in his regular black Mercedes Benz sedan.

As he has grown older, Castro's knees have seemed more wobbly, his step less steady. Nevertheless, he maintains a busy schedule that frequently includes all-night meetings with aides and visitors.

Parliament speaker Ricardo Alarcon, who has been by Castro's side more than four decades, said Thursday he was confident the president would have a speedy recovery.

"He is a man of much strength," Alarcon told international journalists in Havana at a Foreign Ministry ceremony commemorating the founding of the United Nations.

Castro's health has long been closely watched — particularly by his political enemies in Miami, home to a large Cuban exile community.

Such speculation was particularly fierce three years ago when he apparently fainted during a speech under a scorching Caribbean summer sun before a crowd of thousands.

Many people burst into tears after watching Cuba's commander in chief start to collapse behind the podium several hours into that speech on June 23, 2001.

Castro returned minutes later to assure people in the audience — and millions more watching it live on television — that he was fine.

But the incident prompted many average Cubans to reflect for the first time on their leader's mortality and the future of their country after he dies.

The Wednesday night incident seemed far less serious.

Castro on Wednesday asked Cubans to forgive him for "any suffering this may have caused."

Castro noted the presence of international photographers and television camera crews at the event.

"The international press has captured it and surely tomorrow it will be on the front pages of the newspapers," said Castro.

He then encouraged those at the event to continue with their televised musical program, which they did.