"The enemy is always present... in different guises, sizes and shapes," Zuma said in Boksburg, east of Johannesburg.

"OR Tambo warned us all the time," he said, referring to former African National Congress president Oliver Tambo, who had been quoted as saying "beware of the enemy within; remain vigilant".

Zuma, the current ANC president, was addressing the elective conference of the Umkhonto we Sizwe Military Veterans' Association (MKMVA).

He told delegates there were "alien tendencies" within the organisation. These were factionalism, lobbying for positions, ill-discipline, fraud and corruption, gate-keeping and bulk-buying of members.

"We shouldn't allow the organisation to be destroyed in front of our own eyes."

Zuma said people "burning the house in defence of those inside the house" should be stopped.

"There are people who don't like this revolution and are trying to destroy it."

However, even in the face of bitter, negative attacks the ANC had grown. During the ANC's last elective conference in Polokwane in 2007, the party had about 600,000 members, he said.

"When we [ANC leaders] finish this term as we are now, we will have fulfilled the desires of [past] leaders that when we celebrate the centenary we must be a million members. We are more."

Earlier, Zuma MKMVA members welcomed him, singing songs expressing their support for him to serve a second term as ANC president.

"We will walk with Zuma all the way to Mangaung," they intoned, while some held up two fingers, to signify a second term.

ANC Youth League deputy president Ronald Lamola was also at the conference.