SINGAPORE - Singaporeans who turned up at the Singapore General Hospital (SGH) on Sunday to wish former Prime Minister Lee Kuan Yew well were paid a surprise visit by Prime Minister Lee Hsien Loong.

The younger Mr Lee dropped by an area at SGH where hundreds of people have left flowers, handwritten cards and notes dedicated to his ailing father, who has been warded at the hospital with severe pneumonia since Feb 5.

He walked around thanking Singaporeans who had come by to send their affection to the older Mr Lee.

He also obliged their requests for photographs and chatted with them before leaving with his wife, Madam Ho Ching, to visit his father.

Among those the younger Mr Lee spoke to were student Lim Chee Kiang, who had brought a lava lamp which he hoped would "shine" and brighten the get-well area at night.

The 17-year-old student from Delta Senior School said he wishes Mr Lee Kuan Yew a speedy recovery.

"Prime Minister asked me where I stay and how I came here. I told him I took the bus and train," he told reporters later.

The area outside SGH's Block 7 has been piled high with hundreds of flower bouquets, handmade cards, artwork by children, boxes of paper cranes, balloons and soft toys.

SGH had set aside the spot for people to leave their gifts, after some visitors tried to leave them with hospital staff and around public areas in the hospital over the past few weeks.

In a Facebook update on Sunday, Mr Lee said he was grateful to SGH for setting up the corner for messages for his father. "Glad I had a chance to meet and thank well-wishers for their support," he added.

Well-wishers have been going to the hospital in larger numbers since Tuesday, after Mr Lee, 91, suffered an infection and became critically ill.

On Saturday, the Prime Minister's Office said Mr Lee's condition had deteriorated further.

Timeline:

FEB 5: Mr Lee Kuan Yew is hospitalised at the Singapore General Hospital for severe pneumonia.

Feb 21: The Prime Minister's Office (PMO) issues a statement to announce Mr Lee's hospitalisation. It says his condition has stabilised and he is on mechanical ventilation.

Feb 26: Mr Lee's doctors restart him on antibiotics.

Feb 28: Mr Lee's condition improves slightly. He remains sedated and on mechanical ventilation, and is continuing with his antibiotics, PMO says in an update.

March 6: PMO says Mr Lee's condition remains largely unchanged from the last update.

March 13: Mr Lee's condition remains largely unchanged, PMO says.

March 17: Mr Lee's condition worsens due to an infection.

March 18: Mr Lee remains critically ill in the intensive care unit and his condition has deteriorated further, PMO says.

March 19: Mr Lee remains critically ill in the intensive care unit.

March 20: Mr Lee remains critically ill. Prime Minister Lee Hsien Loong would like to thank the public for their support and good wishes, PMO says.

March 21: Mr Lee's condition has worsened, PMO says in a one-line statement.

March 22: Mr Lee's condition has weakened further, says PMO.