Ailing Cuban leader Fidel Castro deplored the defection of three athletes and a coach during the Panamerican Games in Brazil, saying they had betrayed Cuba for dollars.

Cuba's Olympic and world amateur boxing champion Guillermo Rigondeaux and team-mate Erislandy Lara failed to appear for their scheduled bouts in Rio de Janeiro on Sunday.

A member of the Cuban handball team, Rafael Dacosta, and gym trainer Lazaro Lamelas defected earlier, Castro lamented, accusing the United States of luring Cuba's best athletes.

"Betrayal for money is one of the favourite weapons of the US to destroy Cuba's resistance," Castro wrote.

The 80-year-old leader, who has not appeared in public since undergoing intestinal surgery a year ago, has taken to writing to reassert his presence in Cuba and does not miss an opportunity to blast his ideological foe the United States.

Castro also attacked what he called a "Mafia" in Germany that has signed up recently defecting Cuban boxers with contracts for professional fights.

"It uses refined psychological methods and millions of dollars," he wrote.