SINGAPORE - Slightly more than a month after honouring Singapore's first president Yusof Ishak at the National Day Rally, Prime Minister Lee Hsien Loong hosted his widow, Puan Noor Aishah, to lunch at the Istana on Wednesday.

Also there were her son, Dr Imran Yusof Ishak, and his wife Zarina. Mr Lee shared a photograph on his Facebook page of him and Dr Imran shaking hands, with Puan Noor Aishah and Madam Zarina in the background.

He said that he and Dr Imran, who he used to call "Baba", were childhood friends.

"Imran and I used to play together as children, and he taught me how to ride a bicycle. He is now a doctor, working in Brunei. We had a good time reminiscing about our childhood days, and catching up."

At the rally, Mr Lee said Singapore will honour the late former president for his contributions by naming a new mosque, a leading think-tank and a professorship after him.

A new mosque in Woodlands will be named Masjid Yusof Ishak, and the Institute of Southeast Asian Studies (Iseas) at the National University of Singapore (NUS) will be known as Iseas-The Yusof Ishak Institute. A Yusof Ishak Professorship in Social Sciences will also be started at NUS to enhance research in multi-ethnicity and multiculturalism.