Former Singapore president SR Nathan remains critically ill and unconscious, says Prime Minister Lee Hsien Loong.

"But he is restful and his vital signs are currently stable," he said in his latest Facebook posting on Friday, after visiting Nathan at the Singapore General Hospital (SGH).

Nathan, 92, was admitted to SGH last Sunday after suffering a stroke early that morning.

"Also chatted with Mrs Nathan and the family. This is a difficult time for them. The support and encouragement they have received from so many people means a lot to them.


"They have been touched by the many messages and good wishes. Not many people have done as much for Singapore as Mr Nathan has. Please continue to keep him in your thoughts and prayers," Lee further wrote.

Nathan was the longest serving president in Singapore, and was in office for two terms from 1999 to 2011.

He officially stepped down as the sixth president on Aug 31, 2011 and was succeeded by current president, Tony Tan Keng Yam.

Nathan was appointed Singapore's High Commissioner to Malaysia in 1988.