Kao, 84, died of old age, family sources said. He is survived by his wife and daughter.
Kao became the secretary (research) in the Cabinet secretariat, right from the day RAW was formed on September 21, 1968. He had joined the Indian police in 1940 and the Intelligence Bureau in 1947.
He played a key role in connection with intelligence gathering before the 1971 Indo-Pak war and retired from service in January 1977.
After retirement, Kao was appointed senior advisor to prime ministers Indira Gandhi and Rajiv Gandhi.
A very private person, Kao shunned media publicity and refused to write memoirs of his illustrious career.
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