Former Singapore President SR Nathan is in critical condition after he suffered a stroke early Sunday morning.

The 92-year-old is currently admitted in the Intensive Care Unit (ICU) at the Singapore General Hospital (SGH), a statement from the Prime Minister's Office said.

He is the sixth and the longest-serving president of Singapore. Nathan served two six-year- terms as the head of state from 1999 to 2011. He officially stepped down as President on Aug 31, 2011 and was succeeded by President Dr. Tony Tan.

He has also served Singapore as social worker, trade union activist, and diplomat.

In response to this news, President Dr. Tony Tan Keng Yam posted on Facebook that he and his wife Mary Tan, were sad to hear about former President's hospitalisation.

"Our thoughts and prayers are with his wife and family," Dr. Tan posted.

Last year in April, Nathan suffered a stroke and was warded at SGH for almost three weeks. But later he was discharged from the hospital and had been reported to be recovering well.