With just three weeks until a presidential runoff, a leading human rights organization said Monday that the African Union must push longtime Zimbabwe leader Robert Mugabe to end political violence. The 14-nation Southern African Development Community appointed South African President Thabo Mbeki to mediate between Mugabe and the opposition, but those efforts have "not borne any fruit," said Human Rights Watch researcher Tiseke Kasambala. In its report, HRW said it had documented 36 deaths and more than 2,000 injuries at the hands of Mugabe party militants backed by the police and army, but that the real figures may be much higher.

The rights group also said hospitals had been told not to treat victims, scores of opposition activists had been arrested, and homes and businesses of opposition supporters had been looted.

"There's no way a credible runoff can take place unless there are drastic improvements in the remaining weeks," Kasambala, who prepared Monday's report, said in a telephone interview from London.

Opposition leader Morgan Tsvangirai beat Mugabe and two other candidates in the first round of voting March 29, but did not win the 50 percent plus one vote necessary to avoid a runoff, scheduled for June 27.

Tsvangirai's party, foreign diplomats in Zimbabwe, and Zimbabwean and international human rights groups accuse Mugabe of unleashing violence against the opposition to ensure Mugabe wins the runoff. Zimbabwean government and party spokesmen have repeatedly denied such allegations.

The current SADC chairman said there were few options for finding a solution. Zambian Information Minister George Mulongoti predicted the need for mediation would continue after the runoff.

Tsvangirai has called on Mbeki to step aside, saying the South African leader's quiet style of diplomacy has been ineffective and questioning whether Mbeki is biased toward Mugabe.

Mukoni Ratshitanga, a spokesman for Mbeki, said Monday that South Africans "remain seized of the matter, together with the rest of SADC and the rest of the continent."

Mulongoti, the Zambian official, said: "The difficult thing is that Zimbabwe is a sovereign state." He said all fellow Africans could do was "advise" Mugabe.

Whatever the results of the runoff, Mulongoti said it was unlikely they would be endorsed by both sides. Mediation then would be aimed at finding "some transitional arrangements," possibly a unity government, he said.

Mugabe, in power since independence from Britain in 1980, was lauded early in his rule for campaigning for racial reconciliation and building the economy. But in recent years, he has been accused of holding onto power through fraud and intimidation, and trampling on political and human rights.

Zimbabwe's collapsing economy was a major concern of voters during the first round of voting. People are going hungry in what was once the region's breadbasket, with the world's highest inflation rate putting staples out of reach.

The country's economic decline has been blamed on the collapse of the key agriculture sector after the seizures - often violent and at Mugabe's orders - of farmland from whites. Mugabe claimed the seizures begun in 2002 were to benefit poor blacks, but many of the farms went to his loyalists.