THE eldest son of late Cuban leader Fidel Castro killed himself on Thursday after months of treatment for depression.

State media said Fidel Castro Diaz-Balart, who was 68, had been in a “deeply depressed state”.

A brief note read on state television said his treatment had “required an initial hospitalisation then outpatient follow-up”.

The oldest son of Cuba’s late revolutionary leader was known for his resemblance to his father, earning him the nickname Fidelito or Little Fidel.

Castro Diaz-Balart studied nuclear physics in the former Soviet Union and served as scientific adviser to Cuba’s Council of State.

He was vice-president of the Cuban Academy of Sciences and previously led its nuclear programme.

Castro Diaz-Balart was born to Fidel Castro’s first wife, Mirta Diaz-Balart, a woman from Cuba’s aristocracy who Fidel married in his youth before beginning the revolutionary struggle that later brought him and his brother Raul to power.

Because of his maternal lineage, Castro Diaz-Balart is cousin to US Republican Congressman Mario Diaz-Balart, who represents Cuban exiles in Florida.