Police in South Africa have launched a manhunt and questioned dozens of people over the stoning to death of nine suspected illegal miners.

The miners, believed to have come from Lesotho, were stoned to death by suspected rival workers in Matholeville, a western district of Johannesburg, police said on Saturday, denouncing the "barbaric act".

The bodies of the victims "were found lying in the streets of Matholeville" and a tenth person was seriously hurt in the violence on Friday, the police said in a statement.

"We condemn this barbaric attack and we will ensure we leave no stone unturned in making the people of Matholeville and Roodepoort feel safe. The suspects will be arrested as soon as possible and the police will not sleep until we find them," Gauteng police commissioner Elias Mawela said.

"During the night operation, police took in 87 people for questioning and to establish if they are not wanted for any crimes," Mawela added.

Thousands of illegal miners, known as "Zama Zamas" - which means "those who try their luck" in Zulu - operate in the country, according to the South African Human Rights Commission.

Violent clashes between rival groups of workers are relatively common.

South Africa is one of the most violent countries in the world - more than 21,000 people were killed between April 2018 and March 2019, an average of 58 murders a day, according to government data.