For the first time since Singapore's independence in 1965, the ruling People's Action Party (PAP) is seeing the most intense fight in a general election, with contests in all the 89 seats in 29 electoral divisions come polling day on Sept 11.

The electoral divisions comprise 16 Group Representation Constituencies (GRC) and 13 Single Member Constituencies (SMC).

The eight other parties contesting the general election are the Workers Party (WP), Singapore People's Party (SPP), Singapore Democratic Party (SDP), National Solidarity Party (NSP), Singapore Democratic Alliance (SDA), Reform Party (RP), Singaporeans First (SF) and People's Power Party (PPP).

There are three-cornered fights in three SMCs, namely Radin Mas, Bukit Batok and MacPherson.

GE2015 is the republic's first general election after the demise of its founding Prime Minister Lee Kuan Yew in March this year.

This will be the third general election for Prime Minister and current PAP secretary-general Lee Hsien Loong.

By the time nomination closed at noon Tuesday, candidates from all the parties had submitted their papers at nine centres on the island.

Of the 89 PAP candidates, 22 are new faces - 14 of them from the private sector, six from the public sector and two from non-governmental organisations.

Addressing supporters at the nomination centre at Raffles Institution here, Prime Minister Lee, who is defending his Ang Mo Kio GRC seat, called on the people to "vote seriously" for the PAP.

"This (election) is about your future. Vote seriously for the PAP to make sure that we can work together with you, for you, for Singapore," he said.

M. Ravi of the Reform Party is standing against Lee.

WP chief Low Thia Khiang told reporters: "We hope that this election will make people aware of their future and what they should decide for themselves."

The last general election, in 2011, saw contest in 82 of the total 87 seats then. PAP won uncontested in the five-member Tanjong Pagar GRC, led by the late Lee Kuan Yew.