The disruption, caused by protests on the Chinese side of the border, come barely 48 hours after it was revealed that Mongolia had sought $US155 million of allegedly unpaid taxes from Oyu Tolgoi.

The Rio subsidiary that operates Oyu Tolgoi, Turquoise Hill Resources, said the protests had been underway for 10 days and had forced the company to declare force majeure on its copper shipments to Chinese customers.

"The placement of protesters vehicles prevented any traffic from safely traversing the border...and has continued to do so," the company said in a statement.

The focus of the protest was unclear, but Turquoise Hill described the protesters as coal transporters.

It is not the first time tensions on the border between Mongolia and China have caused problems for Oyu Tolgoi.

In December 2016 the Chinese province of Inner Mongolia, which shares a border with the nation of Mongolia, imposed new tariffs on Mongolian goods entering China.

That incident caused copper shipments from Oyu Tolgoi to be temporarily interrupted.

Turquoise Hill owns 66 per cent of Oyu Tolgoi, with the Mongolian government owing the balance.

Rio owns 50.79 per cent of Turquoise Hill, and an expansion of Oyu Tolgoi ranks as arguably Rio's most important growth project worldwide.