Cyril Ramaphosa, who could replace Jacob Zuma as president within weeks, told investors in Davos that "a new mood" had emerged in South Africa.

Ramaphosa took over from Zuma as head of the ruling ANC party in December, and Zuma is under increasing pressure to resign from the presidency.

Ramaphosa, a wealthy former businessman, said that international investors had welcomed his message that a "new era that has been unleashed in South Africa."

"They are wishing us everything of the best -- that we keep to course and follow through with the changes and reforms," he told reporters.

Under Zuma, South Africa has suffered slow growth and record unemployment, with the government engulfed by corruption scandals.

"We are now going to go to the depths of what corruption has been taking place in our state-owned enterprises, I think that is a huge plus," Ramaphosa said.

He said a new graft enquiry and South Africa's criminal justice system would work in parallel "identifying those who have committed wrong and making sure they are brought to book".

Ramaphosa, who has been deputy president since 2014, is looking to revive the economy before elections next year that come amid falling public support for ANC.

On Thursday, he also signalled his opposition to Zuma's plans to build new nuclear plants -- one of the current president's most controversial schemes.

"We have excess power right now and we have no money to go for a major nuclear plant building," Ramaphosa told reporters in Davos.

He earlier told AFP that the transition of political power in South Africa would be handled "delicately, very carefully", without giving any timeline.

"We are talking, we are exchanging views," he said.