Global mining company Rio Tinto says it is severing its ties with Russia, throwing into doubt an aluminium joint venture between it and Rusal, which was founded by oligarch Oleg Deripaska.
In a one-line statement, Rio Tinto said it was "in the process of terminating all commercial relationships it has with any Russian business".
Rio is reviewing its joint venture with Rusal in Queensland Alumina Ltd (QAL) which runs an alumina refinery in Gladstone.
Thursday's decision creates a fuel supply problem for Rio's Oyu Tolgoi project in Mongolia, which relies on Russian diesel.
It comes as more western businesses turn their backs on Russia after the invasion of Ukraine, with Coca-Cola, Pepsi and other big brands joining the rush for the exit in the past 24 hours, amid sanctions that have laid waste to large sections of the Russian economy.
QAL is 80% owned by Rio and 20% by Rusal, where Deripaska continues to hold a stake through their London-listed parent company, EN+ Group.
Deripaska and EN+ were among the oligarchs and companies sanctioned in 2018 by the US government over issues including the invasion of Crimea in 2014.
Activist investors, the Australasian Centre for Corporate Responsibility (ACCR), welcomed the decision by Rio and another Australian company, engineering group Worley, to pull out of Russia.
"We look forward to seeing more detail about the implications for Rio Tinto's Queensland Alumina joint venture," ACCR's director of climate and environment, Dan Gocher, said.
Following Russia's invasion of Ukraine, all Australian companies should sever relationships with companies owned or part-owned by oligarchs aligned with Russian president Vladimir Putin.
"Rio Tinto and Worley should be commended for taking appropriate action."
In a statement to the Australian stock exchange, Worley said it had "begun the safe withdrawal of its services provided in and into Russia and will not enter into new contracts".
The decision will not have a material impact on Worley's global business, the company said.