Zuma (l) is seen as a front-runner in the race to succeed Mbeki (r)

1 Mr Zuma is being investigated in connection with a controversial 1999 $5bn arms deal.

Earlier this year, former ANC chief whip Tony Yengeni was sentenced to four years in prison after receiving a discounted luxury car from one of the companies involved in the deal.

There are allegations every day against senior officials. If they all stepped down, there would be no government Lakela Kaunda Mr Zuma's spokesperson

Scorpions spokesman Sipho Ngwema said that Mr Zuma had until Thursday to answer the questions he had been sent.

Mr Zuma said the leaks had continued over three years "and while the leaks were going on, there was still no official confirmation that I was being investigated.

"I only received confirmation after my lawyers repeatedly wrote to the directorate in this regard," he said.

Denial

He says the rumours that he sought a payment of 500,000 rand ($60,000) a year from French defence company Thales are without foundation.

Mr Zuma is seen as one of the front-runners in the race to succeed Mr Mbeki, who is expected to start his second and final term as president following elections next year.

South African newspapers suggested that the allegations may be linked to a power struggle within the ruling African National Congress.

But his spokesperson, Lakela Kaunda, denied making a quote, attributed to her in the Independent and reported by BBC News Online, seeming to confirm this.

She told the BBC's Network Africa programme that Mr Zuma would not consider stepping down until he was charged.

"There are allegations every day against senior officials. If they all stepped down, there would be no government," she said.