The violence prompted Morgan Tsvangirai to withdraw from a June presidential run-off after winning the March first round of voting. Mugabe claimed victory in the run-off, but it was widely denounced as a sham and last month Mugabe had to sign a power-sharing agreement with Tsvangirai.

The deal, though, has not been implemented because of disputes over who will control which Cabinet posts.

"Justice must not only be seen to be done, but it should be done," Tsvangirai told about 12,000 people in a stadium in Marondera, in a rural northern region known as Mashonaland.

International human rights groups have said Mashonaland suffered high levels of political violence because voters there turned to Tsvangirai's Movement for Democratic Change, angering Mugabe supporters who had seen it as their stronghold.

Tsvangirai did not elaborate on how justice should be done. In the past, he has called for truth and reconciliation hearings which he believes would lead to healing, rather than trials that could lead to jail terms for human rights abusers.

Tsvangirai has said trials could distract from the work of rebuilding Zimbabwe. There are also concerns that Mugabe and his top cronies are stalling implementation of the power-sharing deal as they fear they could be tried for human rights violations.

Leaders of Zimbabwe's neighbouring countries are due in Harare tomorrow to try to persuade Tsvangirai and Mugabe to conclude their power-sharing deal. Tsvangirai has agreed to attend the meeting, though his party has questioned Mugabe's willingness to surrender key Cabinet posts and called for a full regional summit to pressure Mugabe.

Tomorrow's meeting is not a full summit but a meeting of an important committee of the Southern African Development Community. Former South African President Thabo Mbeki, who brokered the stalled power-sharing agreement, was also to attend the meeting.

Tsvangirai has repeatedly accused Mbeki of bias toward Mugabe, saying the South African's refusal to publicly criticise either side amounts to appeasement of Mugabe. "Quiet diplomacy does not mean quiet approval," Tsvangirai said in his speech yesterday.

Zimbabweans are struggling with the world's highest inflation rate and scarcity of food, fuel and other basic goods. The UN predicts half the population will need food aid by next year.

Meanwhile, two civic leaders, arrested more than a week ago in Bulawayo for leading a protest to demand food for the hungry, were spending another weekend in jail because their bail hearing was delayed.

The two, Jenni Williams, 46, and Magodonga Mahlangu, 35, remain in the Mlondolozi Female Prison. The group they lead, Women of Zimbabwe Arise, says the cells are overcrowded and lice-infested.

When they were arrested, they were demanding the immediate formation of a power-sharing government, as well as food for the hungry.

Their group said their continued detention was characteristic of "a regime so terrified of its own people that it has to imprison them".