Leaders from the 14-nation SADC (Southern African Development Community) will meet in Lusaka on Saturday amid increasing concern and impatience over the long delay.

Human rights organisations and the opposition Movement for Democratic Change say Mugabe has unleashed a campaign of systematic violence in response to his biggest defeat.

Mugabe's ZANU-PF party lost control of parliament for the first time and the MDC says its leader Morgan Tsvangirai also won a parallel presidential vote, whose results have not been announced.

An opposition source said Tsvangirai met President Thabo Mbeki of Zimbabwe's powerful neighbour South Africa on Thursday to discuss the crisis. No details were revealed.

Tsvangirai earlier met ruling African National Congress leader Jacob Zuma, who rivals Mbeki as South Africa's most powerful man.

Zuma, abandoning some of Mbeki's trademark "quiet diplomacy" called for the results to be released.

"We urge all parties to respect the will of the people, regardless of the outcome," Zuma said in a speech on Thursday.

"COORDINATED RETRIBUTION"

Amnesty International said in a statement there were widespread incidents of post-election violence in Zimbabwe "suggesting the existence of coordinated retribution against known and suspected opposition supporters".

Amnesty called on SADC leaders to redouble efforts to avoid further deterioration of the human rights situation and urge the Zimbabwean Electoral Commission to release the results.

Human Rights Watch said the Lusaka meeting was SADC's "last real chance" to resolve the crisis in Zimbabwe, whose economy is in ruins.

A quarter of the population have fled to escape hyper-inflation of more than 100,000 percent, chronic shortages of food and fuel and 80 percent unemployment.

The U.S. based body also accused ZANU-PF of increasing assaults on opposition activists and polling agents.

Prospects of any result from the SADC summit are unclear. Critics say the body is a toothless talking shop, too in awe of liberation hero Mugabe to take firm action.

Mbeki, much criticised at home for not taking a stronger line, led failed SADC mediation last year. The crisis has flooded his country with Zimbabwean immigrants, raising xenophobic hostility towards them in South Africa.

But neither Mugabe, known for his uncompromising style, nor the electoral authorities seem ready to buckle. The electoral commission indicated late on Thursday that the results would have to await the outcome of an opposition legal case.

A High Court judge has promised a verdict by Monday on an MDC application to force release of the result.

Tsvangirai has accused Mugabe of a de facto coup to overturn the election result and called on African nations and Western powers to force him to step down, ending his uninterrupted rule since independence from Britain in 1980.

Even though the results remain officially unknown, Justice Minister Patrick Chinamasa said ZANU-PF was preparing for a Mugabe-Tsvangirai runoff -- necessary if neither won more than 50 percent of the first round vote.

Analysts say in a free runoff Tsvangirai, likely backed by third candidate and ruling party defector Simba Makoni and a breakaway MDC faction, would humiliate Mugabe.

But they believe the veteran leader plans to use his powerful security forces and irregular militias, including independence war veterans, to ensure a second round victory.