SINGAPORE - Former prime minister Lee Kuan Yew turns 91 on Tuesday and well-wishers are sending online tributes and greetings to honour him.

There are video montages of the major moments in Mr Lee's life, portraits of him in various media, and several suggestions to declare Sept 16 a national holiday.

The thousands of birthday greetings on social media this year is probably initiated by logo designer Catherine Leck.

On Aug 31, using the hashtag #happybirthdayLKY, she encouraged friends and followers to post online messages for Mr Lee, a founding father who was Singapore's first prime minister.

"I want him to know that even younger Singaporeans who didn't get to see him in action appreciate his efforts," the 32-year-old said.

Her birthday greeting to Mr Lee is an image of his face, made from confetti.

Meanwhile, the People's Action Party, which Mr Lee co-founded, added to the swell of greetings by creating a website - www.happybirthdaylky.org - for people to to post greetings. It also collated the warm wishes of netizens who have used the hashtag.

Mr Lee, in his response, said in a statement on Monday night: "Thank you for your birthday greetings and good wishes. I cannot reply to each greeting individually. I wish you all the very best in return."

The Straits Times understands that he celebrated his birthday with his family last week, before Prime Minister Lee Hsien Loong, his son, began a week-long trip to southern China on Sept 11.