Zimbabwe President Robert Mugabe's spokesman has called reports of a deal in power-sharing talks "nonsense", but both he and South Africa said negotiations over the country's crisis were advancing.

A day after Zimbabwe's two rival parties issued a joint statement calling on supporters to halt violence, Mugabe's spokesman dismissed speculation that an accord was imminent.

"All this talk about an agreement that has supposed to have been reached, which is being reported, is utter nonsense," George Charamba told AFP, saying Mugabe had asked him to relay the message.

"The talks are going on well, and the people of Zimbabwe shall be informed in due course once an agreement has been reached."

Earlier Thursday, a South African government spokesman refused to comment on details of the talks being mediated by President Thabo Mbeki, saying only they were moving ahead.

"The government as mediator won't give details except to say that the negotiations are progressing extremely well," Themba Maseko told reporters.

Power-sharing talks following Mugabe's controversial re-election began in South Africa after Zimbabwe's political rivals signed an accord on July 21 laying the groundwork for negotiations.

The deal set a two-week timeframe for discussions to be concluded, but meetings have extended beyond that deadline.

Talks had broken up on July 29 as negotiators flew home to consult with their leaders amid suggestions by the opposition that discussions on power-sharing between Mugabe and rival Morgan Tsvangirai were deadlocked.

They resumed on Sunday at a secret location in South Africa.