Former Singapore President SR Nathan is in critical condition following a stroke early this morning.

In a statement today, Singapore Prime Minister's Office (PMO) said Nathan is currently in the intensive care unit at the Singapore General Hospital.

Nathan, 92, who was appointed as Singapore's High Commissioner to Malaysia in 1988, was reported to have suffered a stroke in April last year.

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 Singapore President on Aug 31, 2011 and was succeeded by the current President Tony Tan Keng Yam.