The 74-year-old Cuban leader was speaking when suddenly his body could be seen listing off to the side before the government cameras pulled away and concentrated on the crowd.
"Calmness and courage, we lift our flag," Foreign Minister Felipe Perez Roque said, taking the microphone immediately after Castro appeared to faint.
"Companero Fidel obviously has had in the middle of the heat ... a momentary fall," Perez Roque said.
Less than 10 minutes later, Castro was back behind the podium, asking the crowd not to worry, that he was merely tired and would return in the evening to finish his speech.
"Let me rest, sleep a few hours," Castro told the crowd. "Last night I did not sleep at all. I am fine. We will see you tonight."
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