President Jacob Zuma summoned cabinet ministers to a meeting in Cape Town on Tuesday, eNCA television reported, as pressure builds on the embattled 75-year-old leader to quit.

Zuma normally holds cabinet meetings on Wednesdays. It was not immediately clear why Zuma had summoned the meeting a day ahead of schedule.

South Africa's ruling African National Congress (ANC) has called a special meeting of its decision-making executive for Wednesday, at which analysts have said the party could call for Zuma to resign.

Zuma's spokesperson, Bongani Ngqulunga could not be reached for comment.

Zuma, whose presidency has been marred by corruption scandals and economic decline, has been in a weakened position since he was replaced as leader of the ANC by Deputy President Cyril Ramaphosa in December.

He has survived several attempts to oust him in the past. But this time around a significant part of the ANC wants him to step down well before his second term ends mid next year.

Zuma is due to deliver a state of the nation address to parliament on Thursday and faces a new no-confidence vote against his leadership on February 22.

On Monday, Zuma met Zulu King Goodwill Zwelithini, the influential traditional head of South Africa's biggest ethnic group, at the same time that top ANC officials were discussing his future.

A Zulu royal house insider told the Business Day newspaper that Zuma had refused a request from the Zulu king on Monday that he resign. Zuma had declined to resign saying that "if he resigns now it would mean that he would [be] admitting that he had done something wrong", the insider told the newspaper.