SINGAPORE - Emeritus Senior Minister Goh Chok Tong dropped by Mr Lee Kuan Yew's office on Tuesday to wish him happy birthday.

On his 91st birthday, Mr Lee was dressed smartly in a casual red jacket and "looked well and sharp and spoke with a strong voice", Mr Goh reported in a Facebook post.

"Unfortunately, he was having one of those hiccups triggered off by some allergic irritations. Even then, he was getting ready for his Chinese lessons," Mr Goh wrote, adding:

"I cannot help but marvel at the spirit and fight of The Singapore Lion. More good years to you, Mr Lee."

Several other politicians shared anecdotes about Mr Lee online.

Minister of State for Trade and Industry Teo Ser Luck recounted the time Mr Lee asked him a few years ago at a gymnasium how to build up one's core strength.

"Despite some discomfort, whatever I suggested, he tried. Simple request but it reflected Mr Lee's willingness to learn from anyone and his commitment and sacrifice for Singapore," Mr Teo wrote.

Manpower Minister Tan Chuan-Jin also wrote about a resident who conveyed his well wishes to Mr Lee at a Meet-the-People session on Monday night.

"He was quite emotional when he asked me to do so. Thank you for your love and regard for Mr Lee," Mr Tan said.

Other well-wishers include Deputy Prime Minister Teo Chee Hean, Defence Minister Ng Eng Hen and Social and Family Development Minister Chan Chun Sing, who like Mr Lee is an MP for Tanjong Pagar GRC.

Online tributes to Mr Lee continued to pour in throughout Tuesday.

Most came through an online campaign using the hashtag #happybirthdaylky, started by logo designer Catherine Leck, as well as a PAP-launched website to collect well-wishes.

As of 9pm Tuesday, the PAP's Facebook post on Mr Lee's birthday had attracted more than 11,800 likes and over 1,500 birthday greetings.

In the real world, a group of six Lee Kuan Yew fans celebrated his birthday on an inaugural walking tour through sites significant to Mr Lee, like the Istana Park.

At the Sun Yat Sen Nanyang Memorial Hall in Toa Payoh, tour guide Ms Chia Bee Lian, 58, said Mr Lee had once introduced Dr Sun, a revolutionary, as the man who changed China.

One of the participants, a constituent in Mr Lee's ward in Tanjong Pagar, piped in: "Mr Lee is the man who changed Singapore."