The BBC's Will Ross in South Africa - the BBC is barred from Zimbabwe - says it is difficult to verify the numbers of people the MDC claims have been killed, wounded or displaced in recent political violence.
But he says there is evidence that there has been violence, particularly in rural areas - something the MDC accuses the government of orchestrating in a bid to intimidate opposition voters in the lead-up to a possible run-off.
The New York-based Human Rights Watch on Saturday accused Zanu-PF of "using a network of informal detention centres to beat, torture, and intimidate opposition activists and ordinary Zimbabweans".
South African dock workers last week refused to unload a Chinese ship carrying arms destined for Zimbabwe, and a South African court barred its cargo from being transported overland to the border.
On Sunday the 53-member African Union urged Zimbabwe to release the election results "without any further delay", and called for restraint from all parties.
Earlier, UN Secretary General Ban Ki-moon said he would discuss "how to get developments there back to normal" with a number of African leaders on the sidelines of a UN summit in Ghana.
Kofi Annan, his predecessor, has also urged African leaders to do more to address the crisis.
The alarm bells are getting louder but so far they show little sign of making any difference in Zimbabwe, our correspondent says.
Few African heads of state are attending the UN summit in Ghana and it will not be a priority at a conference of the 14-nation Southern African Development Community (SADC), currently taking place in Mauritius.
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