SINGAPORE - A close friend of founding Prime Minister Lee Kuan Yew, Mr Chia Chwee Leong, has died, aged 93.

"Deeply saddened by the passing of Mr Chia Chwee Leong, at the ripe old age of 93. He and my father knew each other for more than 75 years," Prime Minister Lee Hsien Loong shared on Facebook late on Saturday night.

He added: "Their friendship survived the Japanese Occupation, Singapore's independence, marriages, children, grandchildren and widowerhood."

The late Mr Lee met Mr Chia in 1939 when they were both students in Raffles Institution and Raffles College.

They briefly stayed together as dormitory mates at Raffles College. With another classmate, Dr Fong Kim Heng, they watched movies, and made trips to Johor for satay and mee rebus, The Straits Times reported in 2011.

Mr Chia was once the chief government chemist, but left in 1972 to join the private sector.

After he left, Mr and Mrs Lee started visiting his family on the second day of Chinese New Year every year - a tradition that lasted until 2010 when Mrs Lee died.

Both Mr Lee and Mr Chia were reticent about their friendship, until Mr Lee mentioned it in his book Hard Truths in 2011.