Australian iron ore miners, key beneficiaries of China's modern-day industrial revolution, on Tuesday signaled demand growth was finally slowing in response to Beijing's moves to cool its economy.

It was the strongest indication yet from an industry closest to China's phenomenal industrial growth over the last decade that the boom times, if not over, are tempering.

Thanks to the Chinese hunger for iron ore, Australia saw its output go from 80 million metric tons (88.19 million tons) a decade ago to nearly 500 million metric tons now.

BHP Billiton, the world's biggest miner, said it was seeing signs of "flattening" iron ore demand from China, though for now it was pushing ahead with ambitious plans to expand production even further.

Rival Rio Tinto said it too was sticking with plans to lift capacity from its mines in Western Australia's Pilbara iron ore belt, betting on a soft landing for the Chinese economy.

"The (Chinese) economy is shifting, it's changing. Steel growth rates will flatten and they have flattened," Ian Ashby, president of BHP's iron ore division, said ahead of the Global Iron Ore & Steel Forecast Conference in Perth.

China's demand for iron ore, a key steelmaking ingredient, will slow to single digit growth, but the country's annual steel output will still rise by some 60 percent by 2025, Ashby said.

The news knocked the Australian dollar down 1 percent and weighed on stocks in Asia and Europe. Markets are very sensitive to any hint of softening demand in China, given it is Australia's single biggest export market.

China's iron ore imports have grown at a double-digit rate for the last eight years, apart from a 1.4 percent drop in 2010 amid the global financial crisis, according to data from Reuters and China customs.