South Africa's labour ministry on Thursday urged Rio Tinto workers to report instances of discrimination after the Anglo-Australian miner released an internal report detailing sexual assault, racism, and bullying across its mines.

The report, which sparked calls from investors for the entire industry to clean up its act, found that male and female Rio Tinto employees in South Africa experienced the highest rates of racism, at 34.5% and 33.8% respectively, compared to workers in other countries.

Workers at Rio Tinto in South Africa were also the most likely to experience bullying, the report released on Tuesday found, with 54.1% of men and 61.6% of women reporting having been bullied at work.

"We can only encourage those affected to use the protection of our constitution and EEA (Employment Equity Act) to report cases of discrimination to the CCMA (Commission for Conciliation, Mediation and Arbitration) including cases of bullying," the labour ministry said in written responses to Reuters' questions.

Rio Tinto did not immediately respond to a request for comment on the government statement. CEO Jakob Stausholm, who commissioned the report, on Tuesday called the findings "disturbing" and said the company would implement all 26 recommendations from the report.

Rio Tinto's South African subsidiary Richards Bay Minerals extracts and refines heavy mineral sands and produces ilmenite, rutile, and zircon at its site in northern KwaZulu-Natal province.

No-one at Richards Bay Minerals was immediately available to comment.

Asked how prevalent racism, sexism, and bullying are in South Africa's mining industry overall, the ministry said "we are sure that there are many instances of discrimination and bullying in the labour market in general".

However, affected individuals are reluctant to report these cases, the ministry said.

"We must say that it is also encouraging that it is the company that has initiated this research," the labour ministry added, referring to Rio Tinto's report. "What is left is them taking proper action to deal with the findings."

Asked about the report, South Africa's mining industry body the Minerals Council said it and its members "reaffirm their stance of zero tolerance for racism, sexism and gender-based violence in the mining industry".