Fidel Castro on Sunday hailed Nelson Mandela's 90th birthday, calling the Nobel Peace Prize winning icon "a symbol of humanity's highest nobility." "Glory to you Nelson, for 25 years from a solitary prison you defended human dignity!" Castro wrote in a brief note to Mandela that was published in the Communist youth newspaper Juventud Rebelde and appeared in other state-controlled media. "You knew how to resist and, without wanting to or trying to, you became a symbol of humanity's highest nobility." Mandela turned 90 on Friday. Imprisoned for nearly three decades for fighting apartheid, he was release in 1990 and went on to be elected president in South Africa's first democratic elections. Castro, who is suffering from an unknown illness and will tun 82 next month, has not been seen in public since undergoing emergency intestinal surgery in July 2006. His younger brother Raul succeeded him as president in February, becoming Cuba's first new head of state in 49 years.