By Michael Voss

BBC News, Havana



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Cuba's ex-leader Fidel Castro is looking strong and remains on top of developments at home and abroad, says a world health chief.

Dr Margaret Chan, head of the World Health Organization, was granted an audience with Mr Castro this week.

Mr Castro has not been seen in public for more than three years, since a series of major intestinal operations.

The only updates on his health come from visiting dignitaries who have been able to meet him.

Exactly what he suffers from, and where he is recuperating, remain state secrets.

Dr Chan spent more than two-and-a-half hours with Mr Castro on Tuesday evening, when she had a "long talk" with him.

Fidel Castro has not been seen in public for three years

"He walked me out of the house, that's quite a distance, so pretty strong. And don't forget, I'm younger than him," she said, without discussing specific health issues.

Topics ranged from swine flu preparations to the possible health impact of climate change.

Speaking at a news conference in Havana, Dr Chan said that Cuba's 83-year-old former leader remained well informed and as demanding as ever.

"I have to say Mr Fidel Castro's understanding of the importance of health, particularly public health, is impressive.

"Any one of you, especially the doctors, if you don't know your subject well, don't talk to him. He knows more about the subject than you do."