Shintaro Ishihara, who resigned as Tokyo governor on Thursday to return to national politics, is an unrepentant nationalist who relishes the chance to provoke the politically correct.

The 80-year-old is known at home and abroad for his sharp tongue -- aimed at everyone from immigrants to homosexuals, the United States to China.

In a country that sets great store by reticence and understatement, he stands apart as one of the few colourful characters on an otherwise monochrome political scene.

The novelist-turned-politician has been blamed for one of Japan's worst foreign policy crises of the last decade after his plan to buy some uninhabited islands provoked a months-long spat with China.

The national government stepped in to outbid Ishihara, who said he wanted to develop the chain, but not before he had amassed 1.4 billion yen ($17.5 million) in public donations towards the purchase.

Riots and product boycotts followed in China, which has repeatedly sent government ships to disputed waters to press its claim for ownership.

"I think they are insane," Ishihara said of Beijing's moves over islands it calls the Diaoyus, but Japan calls the Senkakus. "The Chinese are saying mine is mine and yours is also mine."

Ishihara has governed Tokyo since 1999, largely enjoying fulsome public support with policies such as banning diesel engines and creating a new-look Tokyo marathon.

He weathered criticism for the amount he spent on a failed bid to host the 2016 Olympic Games and a foray into banking intended to help small businesses that ended badly, but his authority has rarely been in doubt.

He easily won a fourth term in April last year, just weeks after a tsunami crashed into Japan, killing thousands and sparking a nuclear disaster that threatened widespread pollution and large-scale energy shortages.

His bluff public persona and straightforward manner chimed well with an electorate that felt worryingly cast adrift by an absence of strong political leaders.

Born in the western Japanese port city of Kobe in 1932 to a shipping executive, Ishihara achieved fame at only 23 by writing "Season of the Sun", a novel about youths from respectable families exploring the grubby pleasures of the underworld.

The novel, which won the prestigious Akutagawa prize, later became a film that starred both the future governor and his brother, Yujiro, an acclaimed actor who died of liver cancer in 1987.

Ishihara was first elected as a lawmaker in 1968 as a member of the establishment Liberal Democratic Party.

More than a quarter of a century in parliament included time in both the upper and the lower houses and a stint as transport minister.

In 1995 he left national politics, becoming governor of Tokyo four years later.

In a country fond of reticence, Ishihara has repeatedly proved he is unafraid to ruffle feathers and caused uproar in 2010 with his comments on homosexuality.

He told a news conference he believed homosexual people "are missing something, probably something to do with the genes. I feel sorry for them, they are a minority."

He has ridiculed Chinese and Korean residents and once denounced the United States as a nation of "bigots", waging a long public battle for Japanese commercial jets to be able to use a sprawling US base near Tokyo.

He outraged US lawmakers more than two decades ago with his book, "The Japan that Can Say No," in which he described the US military shield around Japan as an illusion and US criticism of Japan as racially motivated.

But it is in China that his pronouncements on shared and complicated history most frequently raise eyebrows.

In 1990, Ishihara told a US magazine: "Japanese troops are said to have engaged in a massacre in Nanjing but it is not true. It is a fabrication by the Chinese side." China says 300,000 people were killed in 1937 as part of the Imperial Japanese army's brutal occupation of a swathe of the country.

Ishihara's son Nobuteru, a senior politician in the LDP, recently made a failed bid for party leadership, being beaten by former prime minister Shinzo Abe in September.