President Jacob Zuma was locked in a "private" meeting with King Goodwill Zwelithini at the Ondini Palace Nongoma in KwaZulu-Natal on Monday.

News24 understands that Zuma arrived shortly after 12:00 to discuss a very private matter with the king.

"I genuinely do not know what the meeting is about, [it is] a very private matter. Nobody knows what it is about," a reliable source told News24.

The source did not want to speculate on whether Zuma was consulting with the king over mounting pressure on him to step down as the president of the country.

Spokesperson for the Zulu royal household, Prince Thulani Zulu, said he could not officially comment at this time.

However, the Presidency described the meeting as a courtesy call.

"This is a longstanding courtesy meeting between the President and His Majesty which was initially meant to take place in January but was postponed due to diary challenges on both sides," Presidency spokesperson Bongani Ngqulunga said.

The meeting with the king comes a day after the top six met with Zuma and allegedly asked him to step down.

African National Congress (ANC) chair Gwede Mantashe on Sunday afternoon said: "We want to ensure that there is stability in the country and stability in the ANC. That is why tonight we are meeting with President Zuma."

It was reported that the intention behind the meeting was not an attempt to humiliate Zuma but to discuss what was best for the country.