A colourful Taiwanese tycoon unveiled plans Thursday to train more than three million "civilian warriors" to help defend the democratic island in the event of a Chinese invasion, donating TW$1 billion ($33 million) of his own money.

Robert Tsao, 75, is one of Taiwan's most successful businessmen and founded major microchip maker United Microelectronics Corp (UMC).

He has been increasingly outspoken against Beijing, and his donation comes after China's forces put on a huge show of force to protest US House Speaker Nancy Pelosi's visit to Taipei last month.

Taiwan lives under constant threat of invasion by China, which claims the self-ruled island as part of its territory to be seized one day -- by force if necessary.

For a week after Pelosi's visit, China sent warships, missiles and fighter jets into the waters and skies around Taiwan, its largest and most aggressive exercises since the mid-1990s.

Tsao warned it would be "an intentional slaughter and vicious war crime and crime against humanity" if China were to use force against Taiwan.

The tycoon said he would put TW$600 million towards training three million "black bear warriors" in the next three years who could work alongside the military.

Another TW$400 million will be used to train 300,000 "marksmen" with shooting skills.

Tsao, who no longer holds any position or title with UMC, portrayed the risk posed by China as existential.

"The Chinese Communist Party's threat to Taiwan is growing and the fight against (it) stands for freedom against slavery, democracy against authoritarianism and civilised against barbaric," he said.

"If we can successfully resist China's ambitions, we not only will be able to safeguard our homeland but make a big contribution to the world situation and the development of civilisation".

Taiwan has spent decades living alongside China's threats, but the sabre rattling has become more pronounced under President Xi Jinping.

China's most authoritarian leader in a generation, Xi is on the cusp of securing an unprecedented third term later this year and has made gaining Taiwan a key part of his "national rejuvenation" goals.

Taiwan remains massively outgunned, with 88,000 ground forces compared to China's one million troops, according to Pentagon estimates.

Mandatory military service for Taiwanese men is currently just four months.

American and Taiwanese strategists have increasingly pushed Taipei to adopt a "porcupine" strategy of asymmetric warfare, which would include training civilians to fight.

Russia's stalled invasion of Ukraine has also focused attention in Taiwan on both the threats posed by a giant authoritarian neighbour and how huge armies can be resisted by a much smaller but determined defender.