Cuban media said Fidel Castro Diaz-Balart had been in a "deeply depressed state'' for several months and "required an initial hospitalization then outpatient follow-up.'' No further details were provided about the circumstances of his death or funeral arrangements.
Fidel Castro Diaz-Balart, a nuclear physicist who studied in the former Soviet Union, he had been working as a scientific counselor to the Cuban Council of State and Vice-president of the Cuban Academy of Sciences at the time of his death.
Castro, 86, said last month he would step down as President in April. He took over in 2008 after his brother Fidel Castro, who had governed Cuba since leading the 1959 revolution, became seriously ill. Fidel Castro died in 2016.
Raul Castro, 86, had previously said he would step down in February at the end of a months-long political cycle in which voters and government officials pick the members of local, provincial and national assemblies and the members of the powerful council of state.
The Cuban government on Wednesday selected 57-year-old First Vice President Miguel Mario Diaz-Canel Bermudez as the sole candidate to succeed Raul Castro. It is the first time in almost sixty years that a Castro will not be the president of Cuba.