Mr Zuma's spokesman Bongani Ngqulunga said:

It's rumours and gossip and we don't comment on them at all."

Mr Ramaphosa is a front runner in December's African National Congress (ANC) leadership contest to takeover from Mr Zuma.

The president is known to favour Nkosazana Dlamini-Zuma, his ex-wife, to become the leader of the governing party.

Asked in parliament on Thursday whether he might be sacked, Mr Ramaphosa had declined to speculate but said if he was he would accept the president's decision.