The popular eldest son of the late Cuban president Fidel Castro committed suicide on Thursday, state media reported. He was 68 years old.

"Fidel Castro Diaz-Balart, who had been treated by a group of doctors for several months due to deep depression, took his life this morning," Cuba's official newspaper Granma reported.

"Fidelito" -- as he was known on Caribbean island nation -- had initially been hospitalized for his condition and then continued with outpatient follow-ups.

Born on September 1, 1949, he was the son of the revolutionary Castro's first marriage to Mirta Diaz-Balart.

Castro Diaz-Balart had served as scientific adviser to the Council of State and was vice president of the Cuban Academy of Sciences. He studied nuclear physics in the former Soviet Union and at one point was head of Cuba's nuclear program. He preferred to stay away from political issues.

In his most recent public appearances Castro gave lectures on nanoscience, in which he specialized.

The younger Castro was very popular in Cuba even though he never held a political position. He bore a strong resemblance to his father: both were tall and had bushy beards.

Many Cubans remember him as a little boy dressed in an olive drab military uniform, accompanying his father on January 8, 1959 as he entered Havana triumphantly after the revolution.

The younger Castro was always faithful to his father's communist ideals.

His death came 15 months after that of his father at the age of 90.

At that funeral, Castro was seen standing alongside five half-siblings that his father had with another woman, Dalia Soto del Valle.

Funeral arrangements will be made by the family, state media said.