The 71-year-old former deputy prime minister, seen a proxy for the ruling party, won by just 7,269 votes over his closest challenger out of 2.1 million valid votes cast in Saturday's four-way race to become head of state.

Tan got 744,397 votes, or 35 percent of the total, well below the 60 percent garnered by the ruling People's Action Party (PAP) in general elections held in May that marked the lowest point in its popularity after 52 years in power.

"The president is a president for all Singaporeans, not only for those who have voted for me but even for those who have not voted for me. I pledge to work for each and everyone of you," he said after his victory was announced.

The Elections Department ordered the recount of all votes cast after the first tally showed the two frontrunners were less than two percent apart.