Mr Gupta, who leads the GFG Alliance which recently bought the Australian steelmaker and mining group Arrium, is understood to be checking out Rio's PacAl assets at Gladstone in Queensland this week.

Rio's PacAl assets are the Boyne Smelter and nearby Gladstone Power Station, Bell Bay Smelter (Tasmania), Tomago Smelter (New South Wales) and NZAS smelter in New Zealand. Their value has been speculated at $US1 billion or greater.

Other companies have expressed some interest in Rio's PacAl business in recent years, but have walked away.

The Boyne smelter is the largest aluminium smelter in the country, producing more than 500,000 tonnes of aluminium per year.

Mr Gupta, who has been applauded for securing the jobs of more than 5500 Arrium workers, has in the past revealed he is interested in making more investments in Australia.

"Looking forward, we will continue to explore opportunities to further grow our presence in Australia in adjacent and complementary industries, including renewable energy, metals and mining," he said in July.

Representatives of Mr Gupta and Rio Tinto would not comment on the speculation on Tuesday.

But Rio chief executive Jean-Sebastien Jacques gave an indication about his attitude towards asset divestment in August, when he said: "For sure, I want to clean up the portfolio as quickly as I can, but at the same time there will not be a fire sale...we want to build over time a portfolio of world-class assets by exiting some of our non-core assets, and at the same building new world-class assets."

Media speculation of Mr Gupta's possible interest in aluminium emerged as Rio said better rail capacity and improved productivity helped lift iron ore shipments and production for the September quarter.

In its latest operations review Rio said it was on track to meet its guidance for Pilbara iron ore shipments for 2017 of "around 330 million tonnes". Iron ore shipments were up 11 per cent on the June quarter to 85.8 million tonnes, and iron ore production up 6 per cent.

Shares in Rio continued their strong rise on Tuesday, closing 91 cents higher at $71.46, their highest closing price since February 14, 2013.

The climb came despite Rio cutting significantly its production guidance for mined copper to between 460,000 and 480,000 tonnes. Previously, it had forecast annual production of 500,000 to 550,000 tonnes.

The company also said investigations were underway into a fatality this month at the Rio Tinto Kennecott smelter in America.

Rio also said its bauxite production for the quarter was 12.9 million tonnes, while lifting its bauxite production guidance to between 50 and 51 million tonnes.

"The business performed very well in the September quarter, with a strong quarterly production performance and a wave of productivity improvements," Mr Jacques said.

"We continue to shape our asset portfolio and announced $2.5 billion of additional returns to shareholders from the proceeds of the Coal & Allied sale, demonstrating the robustness of our strategy and ability to invest in high-value growth whilst returning excess cash to shareholders," he said.

Peter O'Connor, senior analyst at Shaw and Partners, said the numbers "look okay," after assessing Rio's quarterly report.

Mr O'Connor also said Rio had recorded a miss on copper, but acknowledged that the Escondida mine in Chile was "coming back", although this was slower than hoped, after a long-running labour strike earlier this year.

"Another quarter of disappointing copper performance slips by???if it's not strikes, sovereign risks, grade, and ramp-up its weather. This chunky capital base needs to start earning its return on capital. No more excuses," he said.