Hundreds of thousands of Vietnamese lined the streets Sunday for the funeral of independence hero General Vo Nguyen Giap who orchestrated the country's stunning wartime victories over France and the United States.

Military trucks carrying Giap's flag-draped coffin through Hanoi were met by vast crowds -- at places 10 or 20 deep -- with many mourners falling to their knees to pray as the cortege passed.

"Long live General Giap!" some shouted as the funeral procession drove to the airport, where his body was flown to his native Quang Binh province some 500 kilometres (310 miles) away for burial.

Hordes more people, many holding photographs of the general or bunches of yellow flowers, greeted the coffin's arrival in Quang Binh and lined sections of the main highway from the airport to the remote site where he was due to be buried later Sunday.

Giap, who died aged 102 on October 4, was the architect of Vietnam's battlefield victories over France and the US and the one-party communist state has keenly tried to co-opt the popular general's legacy to bolster its own legitimacy.

"(Giap) is the general of the People and his name will be forever engraved in the history of the nation," Communist Party leader Nguyen Phu Trong said in a televised speech on Sunday.

His death was "a great loss" for Vietnam, he added, speaking before the procession at the Hanoi Funeral House, where the general's body lay in state overnight.

Giap, who became a prominent government critic late in life, is second only to founding president Ho Chi Minh in the communist nation's affections.

He has been honoured with two days of national mourning -- when all flags fly at half mast -- and the largest state funeral in decades.

"The General gave his whole life to the country and the people," his son, Vo Dien Bien, said in a short, emotionally-charged speech in Hanoi on Sunday.

"Now he is gone, his spirit will join with those of the Vietnamese people, giving (them) strength to build a strong and prosperous country."

Vietnamese have flocked to pay their last respects to Giap, lauded as a military genius for the guerrilla tactics that inspired resistance movements around the world.

The former history teacher turned military commander, led his troops to victory over France in 1954 at Dien Bien Phu -- the battle that ended French involvement in Indochina -- and played a key role in Vietnam's defeat of the United States in 1975.

"He's gone, taking with him part of our glorious victory," said retired civil servant Tran Hung Tuy, 74.

"This is the biggest funeral since the death of President Ho Chi Minh in 1969," he told AFP after finishing a prayer as the coffin went past.

The enormous crowds are highly unusual in authoritarian Vietnam, which heavily stage-manages anniversary events and routinely breaks up political protests with force.

Despite being politically marginalised after the country's reunification in 1975, Giap remained a national icon -- even among those born after the war.

"So many people cried -- it is completely different from previous (state) funerals," war veteran Vu Phi Hung, 62, told AFP.

"This shows that the people had a deep, strong emotional connection with Giap," he added.

Until well into his 90s Giap, physically frail but outspoken, wrote open letters and used anniversary events to rail against sensitive issues such as corruption and mining.

In so doing, the general provided implicit cover for party critics and the country's dissidents, experts said -- despite always remaining a loyal party member.

Speaking in Hanoi on Sunday, Party leader Trong also acknowledged Giap's "important opinions on the country's major issues".

General Giap is survived by Dang Bich Ha, his wife since 1949, and four children.