Singaporeans are bidding a final farewell to founding prime minister Lee Kuan Yew following a week-long mourning.

Lee's coffin will be carried across the city after which a state funeral will take place at 14:00 local time. His body will then be cremated in a private ceremony led by his family members.

The state service will be attended by several dignitaries from across the world including former US president Bill Clinton, Australian Prime Minister Tony Abbott, Indian premier Narendra Modi, Japanese Prime Minister Shinzo Abe, Indonesian President Joko Widodo, South Korean President Park Geun Hye, and Thai Prime Minister Prayut Chan-o-cha.

"Since my father passed away, Singaporeans have expressed their grief overwhelmingly. Huge crowds have come to the community tribute centres, and queued up for hours, day and night, to pay their respects at Parliament House.

Overseas and online, our friends and Singaporean clubs have also sent their condolences and organised memorial events to honour my father. It has been a deeply moving experience," said Singapore's current Prime Minister Lee Hsien Loong in his tribute.

Lee's body has been lying in state in Parliament House since 25 March and more than a million people have paid their respects.

Lee, hailed as the father of Singapore, died on 23 March due to severe pneumonia at the age of 91.

Singaporeans are braving heavy downpours with scores of people lining up along the streets to pay their tributes.

"Mr Lee's leadership and dedication have touched many of us and given us better living and working conditions. This is the least we can do for him," Gary Haris, 40, who has been standing on the street since morning, told Asia One.

Most of the businesses across Singapore are expected to be shut to mark Lee's funeral. Hundreds of security personnel have also been deployed on the streets to ensure a smooth procession.

Lee stepped down in 1990 after 31 years of being prime minister during which he oversaw the country's independence from Britain and its severance from Malaysia. Lee is widely regarded as a towering statesman.