South Africa's mines will be nationalised and land will be expropriated, ANC Youth League deputy president Ronald Lamola said on Monday.

"Leadership of the ANC might be afraid to say 'nationalisation' and 'expropriation of land without compensation', but the policy conference has clearly demonstrated the power and the mobility of the young lions," Lamola said in Johannesburg.

"The policy conference [of the ANC held in June] had unanimously, clearly stated that the strategic mines of South Africa must be nationalised for the benefit of all South Africans."

Lamola was reporting back on the ANC's policy conference, the role of the youth league, and reflecting on former President Nelson Mandela's contribution to the struggle.

"Comrades, we have won the debate on nationalisation," he told the league's Dr Mxolisi Majombozi branch at the University of the Witwatersrand.

"Even the African National Congress... they say we are at the point where we must look in terms of which minerals to nationalise."

Lamola urged young professionals to play their part by suggesting which minerals needed to be placed in the state's hands as part of the fight for "economic freedom".

"We have stated with this opportunity that has been given to us that we must now identify strategic minerals to be nationalised," he told the cheering crowd.

He said land should be given back to its rightful owners.

"The policy conference has also stated clearly that the expropriation of illegally taken land by the Boers and the British colonies must be expropriated without compensation," Lamola added.

"[We] should thank branches of the ANC that they have now taken it upon themselves to fight for economic freedom."

Lamola said the Youth League should defend its views and ensure these were made policy at the ANC's elective conference, to be held in Mangaung in December.

Earlier on Monday, ANC secretary-general Gwede Mantashe rejected wholesale nationalisation.

"Wholesale nationalisation is not an option, it's costly, it's unsustainable."

The party did however support state intervention in the economy.