Three People's Action Party (PAP) candidates have been declared winners.
Sample count results, released publicly for the first time by the Elections Department (ELD), showed PAP in the lead in 26 out of the 29 electoral divisions, and by a massive margin of more than 70 per cent of the votes in 15 of them, according to media reports.
Prime Minister Lee, 63, was re-elected from his group representation constituency (GRC) of Ang Mo Kio. A GRC is a type of electoral division or constituency in Singapore where the MPs are voted into Parliament as a group.
"My team and I in Ang Mo Kio - some of us have served you for many years, some of them are new. Regardless, we'll work together and work hard to build a better home, and we'll speak up and represent you in Parliament."
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"We will also represent Singaporeans to build a better Singapore," Lee said.
"The sample count results have been really encouraging across the island, but we don't want to take them for granted, just as we should never take our residents for granted," PAP candidate Tan Chuan-Jin was quoted as saying.
More than 2 million Singaporeans voted today in one of the biggest general election contest.
Opposition politicians have challenge the government on issues related to migrants, cost of living, low wages, foreign workers competing for jobs, the stressed transportation system and the age limit on retirees to withdraw Central Provident Fund, a compulsory savings from salaries.
Politics in the city-state since its independence in 1965 has been dominated by the ruling PAP founded by Lee Kuan Yew, father of Lee, and it has won every election.
The opposition is made up of Workers' Party, National Solidarity Party, Singapore Democratic Party, Reform Party, Singaporeans First, Singapore People's Party, Singapore Democratic Alliance and People's Power Party.
In previous elections, the PAP has retained some of its seats without a vote -- known as a walkover -- as no opposition candidate ran against them. But this year every seat in the compulsory election is being contested.