Koch Industries has confirmed David Koch, who was last year named the 11th-richest man in the world, has died aged 79.

Key points: David Koch's death was announced by his brother via a company statement

David Koch's death was announced by his brother via a company statement The brothers were worth an estimated $71 billion each, having inherited Koch Industries from their father

The brothers were worth an estimated $71 billion each, having inherited Koch Industries from their father Mr Koch was known for supporting conservative causes and was the Libertarian Party's vice presidential candidate in 1980

Charles Koch (pronounced 'coke') announced his brother's death in a statement on the company's website.

"Twenty-seven years ago, David was diagnosed with advanced prostate cancer and given a grim prognosis of a few years to live," he said.

"David liked to say that a combination of brilliant doctors, state-of-the-art medications and his own stubbornness kept the cancer at bay.

"We can all be grateful that it did, because he was able to touch so many more lives as a result."

David Koch retired last year from his roles at Koch Industries and associated companies due to poor health.

One half of powerful duo

The two brothers were estimated to be worth $US50.6 billion ($71.3 billion) each, with Forbes ranking them as the 11th-richest men in the world last year.

Their father, Fred Koch, founded Koch Industries and built gas plants in Josef Stalin's Soviet Union before becoming an ardent anti-communist and a founder of the archconservative John Birch Society.

Koch Industries was involved in oil refining, chemicals, biofuels, pipelines, commodities trading, ranching, fertiliser and paper.

It made everyday products such as disposable cups, paper towels, carpet and stretchy Lycra fabric.

David and Charles Koch were best known for a vast political network they built that became popularly known as the "Kochtopus" for its far-reaching tentacles in support of conservative causes.

The pair founded the anti-tax, small government group Americans for Prosperity and donated heavily to Republican candidates.

They helped back the conservative Tea Party movement that arose after Barack Obama took office and fought his policies, including the 2010 Obamacare healthcare law that reduced the number of Americans without medical insurance by millions.

Critics said the brothers used their riches to buy political influence and peddle positions that would benefit them financially.

David Koch ran unsuccessfully for US vice-presidency in 1980 as a Libertarian Party candidate.

His campaign called for abolishing income taxes, minimum wage laws, government regulatory agencies, the social security retirement program, the FBI and the CIA.

Millions donated to cancer research

Mr Koch was a generous donor to conservative political causes as well as educational, medical and cultural groups.

In 1991, David survived a plane collision in Los Angeles that killed 34 people.

"I felt that the good Lord spared my life for a purpose," Koch told New York magazine in 2010.

"And since then, I've been busy doing all the good works I can think of."

He donated $100 million in 2007 to create the David H Koch Institute for Integrative Cancer Research at the Massachusetts Institute of Technology (MIT).

Mr Koch was last year ranked as the world's 11th richest man, tying with his brother. ( Reuters: Lucas Jackson )

He also gave millions to Johns Hopkins University in Baltimore, the Memorial Sloan-Kettering Cancer Centre in New York City, the MD Anderson Cancer in Houston and other institutions.

"When I pass on, I want people to say, 'he did a lot of good things, he made a real difference, he saved a lot of lives in cancer research'," he told The Weekly Standard following the 2012 Republican convention.

An engineer who studied at MIT, Mr Koch joined Koch Industries in 1970 and served on its board.

He also served as chief executive officer of Koch Chemical Technology Group, LLC, a Koch subsidiary.

Rift between brothers

Two of the four Koch brothers, Frederick and Bill Koch, sued the other two, claiming in a 1998 trial that they were cheated out of more than $US1 billion when they sold their stake in Koch Industries back in 1983. David and Bill Koch are twins.

The dispute stemmed from a falling out three years earlier when Bill Koch criticised Charles's management of the company, and with Frederick's support, tried to gain control of the company's board of directors.

After the takeover move failed, the board fired Bill as an executive.

Bill and Frederick Koch and other dissident stockholders sold their interests, and the brothers later sued claiming the company withheld crucial information that would have led to a higher sale price.

Bill and Frederick lost their case, but the lengthy public trial offered a rare behind-the-scenes glimpse at the Koch family.

The Kochs' father, Fred Koch, guessed early — before two of his boys were out of nappies and before two were even born — that wealth might split his family apart.

"It will be yours to do with what you will," the father wrote in a 1936 letter to his two oldest sons.

"It may be either a blessing or a curse."

David Koch and his wife, Julia Flesher, have three children.

Reuters/AP