Cuban revolutionary leader Fidel Castro, who has been out of the public eye for more than two months, is working on a book with Venezuelan President Hugo Chavez and is not at death's door, a pro-government blogger said on Wednesday.

Yohandry Fontana, who often is first to report official information and viewpoints, attacked a Barcelona-based blog and other social media for spreading the idea that Castro, who turned 86 on Aug 13, is seriously ill, and said there was "bad news" for them and "the creative boys of the CIA".

"Fidel Castro is working together with Hugo Chavez on a book that will appear soon," Fontana wrote.