Security forces rounded up more than 200 mostly undocumented foreign nationals allegedly involved in illegal mining in South Africa on Tuesday, police said, in a major anti-crime operation involving the military.

The swoop on a gold mine shaft west of Johannesburg was part of an operation announced by President Cyril Ramaphosa in February that deployed the army to assist police fight illegal mining and gang violence in crime hotspots.

It involved police, soldiers, and private security, and resulted in the arrest of 217 people, more than 100 of whom were undocumented migrants from Lesotho, police said.

Mozambicans, Zimbabweans and South Africans were also arrested, and firearms and ammunition confiscated, a statement said.

'Operation Prosper'

Ramaphosa said organised crime was the "most immediate threat" to South Africa when he launched Operation Prosper to deploy 2,200 soldiers alongside police.

Thousands of unregistered miners operate in South Africa, scavenging abandoned mines for gold and other minerals in arduous and often perilous conditions.

Tuesday's raid comes as South Africa is cracking down on undocumented migrants, with thousands returning home in recent weeks in response to a campaign by local groups who claim foreign nationals are taking South Africans' jobs.