Tens of thousands of mourners braved torrential rain, howitzers fired a 21-gun salute and jet fighters screamed across the sky Sunday as Singapore staged a grand funeral for its founding leader Lee Kuan Yew.

"The light that has guided us all these years has been extinguished," his son, Prime Minister Lee Hsien Loong, told a state funeral at the National University of Singapore attended by Asia-Pacific leaders.

Lee's coffin, draped in the red-and-white national flag and protected by a glass case atop a two-wheeled gun carriage, was earlier taken in a procession from parliament pulled by a ceremonial Land Rover as a rain-soaked crowd chanted his name.

Four F-16 fighters from the air force's Black Knights aerobatic team performed a fly-past -- with one peeling off to symbolise a "missing man" -- as the cortege made its way through a square where Lee was first sworn in as prime minister in 1959.

He kept the position for 31 years, ruling with an iron fist to transform Singapore from a sleepy British colonial outpost into a gleaming metropolis that now enjoys one of the world's highest standards of living.

Singapore became a republic in 1965 after a brief and stormy union with Malaysia. Lee, 91, died less than five months before the island celebrates its 50th anniversary as a nation.

A 21-gun salute is normally reserved for sitting heads of state but an exception was made for Lee.

'Our national hero'

After the eulogies ended at the state funeral, civil defence sirens sounded across the island to signal the beginning and end of one minute of silence.

The funeral ended with the singing of the Malay-language national anthem "Majulah Singapura" (Onwards Singapore).

"He is like a father to all Singaporeans, the past, present and future generations," said Tan Yen Lee, 26, a staff nurse at the Singapore General Hospital where Lee died Monday after a seven-week confinement for severe pneumonia.

"We have seen over the last week amazing scenes, a massive outpouring of emotion for our national hero, and it culminates today."

People wept openly, waved flags and threw flowers on the street as the motorcade drove through districts associated with the political career of the British-trained former trade union lawyer.

Officials said more than 450,000 people -- in a nation with just 3.34 million citizens -- had paid their last respects to Lee by the time his public wake ended in parliament on Saturday night.

On Sunday strangers huddled together under umbrellas as they waited patiently along the 15-kilometre (10-mile) funeral procession route.

Families including babies and grandparents turned up early to secure choice spots, bringing umbrellas and plastic ponchos in anticipation of rain.

"We are here today as a family to witness this historic moment. As Singaporeans we may have our differences, but when it comes to a crunch we stand together. That is what Singapore is about and that is Mr Lee's legacy," said teacher Joel Lim, 35.

Lee stepped down in 1990 in favour of his deputy Goh Chok Tong, who in turn was succeeded by Lee's son.

Reconciliation call

Former US president Bill Clinton and Lee's close friend former US secretary of state Henry Kissinger, Japanese Prime Minister Shinzo Abe, South Korean President Park Geun-Hye, Australian Prime Minister Tony Abbott, Indian Prime Minister Narendra Modi, Cambodian Prime Minister Hun Sen and Indonesian President Joko Widodo were among the dignitaries in attendance.

Former foreign secretary and Leader of the House of Commons William Hague represented old colonial ruler Britain.

Lee is revered by Singaporeans for his economic and social legacy but criticised by rights groups for sidelining political opponents, muzzling the press and clamping down on civil liberties. A number of his opponents went bankrupt due to costly libel damages or went into self-exile.

Phil Robertson, deputy Asia director for Human Rights Watch, called on Singapore to mark Lee's passing by "making a break from the politics of yesteryear" while remembering his achievements.

"The government should start by reconciling with many of the exiles who have been persecuted and pushed away for far too long," he said.

Singapore now has one of the world's highest GDP per capita incomes at $56,284 in 2014, up from a mere $516 when it gained independence.

Ninety percent of Singaporeans own their homes, thanks to a public housing scheme launched by Lee, and the country enjoys one of the world's lowest crime rates.

Its highly paid civil service is consistently ranked among the world's most honest.