Nancy Wake, Australia's greatest World War II heroine and a prominent figure in the French Resistance known as the "The White Mouse" for her ability to evade the Germans, has died in London.

Australian Prime Minister Julia Gillard said the woman who was once the Gestapo's most wanted person, was "a devastatingly effective saboteur and spy".

"Nancy Wake was a woman of exceptional courage and resourcefulness whose daring exploits saved the lives of hundreds of Allied personnel and helped bring the Nazi occupation of France to an end," Gillard said.

Wake, who died in a London hospital on Sunday just days short of her 99th birthday, was the nation's most decorated servicewoman from WWII, holding France's Legion d'Honneur, Britain's George Medal and the US Medal of Freedom.

Born in Wellington, New Zealand, she grew up in Australia and politicians in both countries led tributes to the woman who survived several firefights with the enemy, being shot at in a pursuit and a brief imprisonment during the war.

New Zealand's Veterans' Affairs Minister Judith Collins described Wake as "a woman of exceptional courage and tenacity, who cast aside all regard for her own safety and put the cause of freedom first".

Australian National Party leader Warren Truss said Wake's heroic achievements "are the stuff of legend".

"And all Australians feel very proud of this wonderful woman," he said.

Wake ran away from home aged 16 and by the early 1930s was living in Paris, where she worked as a journalist.

Witnesses to the rise of fascism in Europe, Wake and her wealthy industrialist husband Henri Fiocca joined the fledgling Resistance after France's surrender in 1940.

She once described a visit to Austria in 1933 as a first-hand look at Nazi cruelty.

"In Vienna they had a big wheel and they had the Jews tied to it, and the stormtroopers were there, whipping them. When we were going out of Vienna they took our photos. That was my experience of Hitler," Wake said.

Wake and her husband helped Allied servicemen and Jewish refugees escape into Spain before she took her partner's advice and fled to England in 1943, where she began work in special operations.

She parachuted back into France in April 1944 before D-Day, tasked with helping distribute weapons to Resistance fighters.

"In those days it was safer, or a woman had more chance than a man, to get around, because the Germans were taking men out just like that," she later recounted.

Wake was never to see Fiocca again, learning only after the liberation of France that he had been killed by the Gestapo in August 1943.

After the war, Wake returned to Australia in 1949, where she made several failed attempts to win a seat in parliament.

She went back to England, where in 1957 she married RAF officer John Forward, but the couple settled in Australia within two years, living there for the next four decades until Forward's death in 1997.

Restless again, Wake left Australia for England in 2001 with the intention of remaining there for the rest of her life.

The fearless heroine was made a Companion of the Order of Australia in 2004, praised for her outstanding actions in wartime.

She is expected to be cremated privately and her ashes scattered at Montlucon in central France, scene of her 1944 heroism.