President Thabo Mbeki has expressed concern about corruption allegations surrounding his deputy, Jacob Zuma, calling for a speedy resolution to the investigation by the Scorpions.

While Mbeki was speaking, Durban businessman Shabir Shaik was being questioned in Durban by Scorpions investigators. He faces a range of questions on various topics, including his business relationship with Zuma and former transport minister Mac Maharaj.

The Scorpions have called on Zuma to answer a wide-ranging set of questions in relation to his alleged involvement in the multi-billionrand arms deal.

They form part of a broader probe into the investigations unit's longstanding investigation into the controversial arms acquisition.

Zuma has until tomorrow to answer a list of 35 questions. He has not yet indicated whether he will co-operate, having reacted angrily to the questions being leaked to the Sunday Times, saying the leak was "totally unacceptable and despicable".

Zuma said they had cast aspersions on his character, leading him to question the motives of the investigators. Officials close to the president have hinted that political motives are behind the leaks, especially in the run-up to next year's elections.

Mbeki said yesterday the issue of political motivation was of concern, but he could not comment on the investigation as it had to run its course.

"Of course I am concerned about this. I am concerned about the mere fact of the allegation. (But) I do not know who is right and who is wrong."

Mbeki said he had spoken to Justice Minister Penuell Maduna, indicating that the sooner the matter was concluded, the better.

"I do hope they can move it (ahead swiftly)," he said.

With acknowledgements to Robyn Chalmers, Tim Cohen and the Business Day.