An Indian billionaire is forging ahead with a massive coal mine in Australia that activists say will be a disaster for the environment.

Gautam Adani said Tuesday that he had given the "green light" to his firm's $12 billion coal project in Australia's northeastern Queensland state.

"This is the largest single investment by an Indian corporation in Australia, and I believe others will follow with investments and trade deals," Adani said in a statement.

The Adani Group is also building a 240-mile railway line and an airstrip at the mine, which it says will create at least 10,000 new jobs.

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Environmental groups and many politicians are bitterly opposed to the project, saying it will lead to the destruction of the environment. Greenpeace Australia described it as a "death sentence" for the Great Barrier Reef.

"The people of Australia have overwhelmingly rejected this toxic project," Greenpeace campaigner Nikola Casule said in a statement on Tuesday. "The age of coal is dead and we need real leadership to ensure a just transition away from fossil fuels."

India, where Adani is planning to ship most of the Queensland coal, is trying to make that transition despite still relying on coal for 60% of its power. The Indian government is targeting a tenfold increase in solar energy capacity by 2022, and solar power is now cheaper than electricity from coal fired power stations.

"It doesn't make sense to be planning huge long-term investments in coal when we have surplus power production and rapidly falling cost of renewable power," Vinay Rustagi, managing director of energy consultancy Bridge to India, told CNNMoney. "It is hard to see any merit in this news from an Indian perspective."

Adani doesn't see it that way. He says the project will relieve "energy poverty in India," where 300 million people still aren't connected to the electricity grid.

President Trump singled out India and its growing coal industry during a speech last week outlining his decision to end U.S. involvement in the Paris Agreement on Climate Change. India fired back on Tuesday and reiterated its commitment to the Paris accord.

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Environmental damage isn't the only aspect of the project ruffling feathers in Australia.

A proposal to use Australian taxpayer money has also caused outrage. The Adani project stalled last month due to a lack of tax concessions from the Queensland government, but the two sides reached an agreement last week.

Queensland lawmaker Larissa Waters, who has consistently opposed the project, slammed Tuesday's announcement as a "PR stunt."

Adani's despo PR stunt to squeeze $1bn out of Australian taxpayers isn't fooling anyone. Together we'll stop them. #StopAdani pic.twitter.com/GwM4nz17aK — Larissa Waters (@larissawaters) June 6, 2017

Adani said he would push on despite the protests.

"We have been challenged by activists in the courts, in inner city streets, and even outside banks that have not even been approached to finance the project," the Indian tycoon said. "We are still facing activists. But we are committed to this project."

-- Karma Gurung contributed to this article.