"That is reading too much into an opinion which does not reflect what we are witnessing on the ground," Madhuku said.
Tsvangirai's Movement for Democratic Change (MDC), human rights groups and Western powers accuse ZANU-PF of launching a campaign of post-election violence.
Tsvangirai says 10-15 MDC supporters have already been killed in the crackdown.
The opposition leader says he won the presidential election outright and Mugabe's 28-year rule is over.
The government has clearly indicated it expects a runoff - necessary if neither candidate wins an absolute majority. Such a vote would be held three weeks after the result is announced.
Further muddying the waters, Zimbabwe postponed an annual summit of Africa's COMESA trading bloc which it was due to host in the first half of May - suggesting the government may expect electoral developments in that period.
Cape Town Archbishop Thabo Makgoba called for a U.N. arms embargo against Zimbabwe, saying the plight of its people was heartbreaking.
He said the delay in releasing election results eroded "any remaining trust the people may have in the electoral process".
The South African army said there had been a clear increase in the number of people fleeing Zimbabwe since the election with almost 1,800 illegal immigrants caught at the border. Millions of economic migrants have already fled.
Zimbabwe's neighbours, previously passive despite the collapse of the country's economy, this week took a harder line towards Mugabe, refusing to allow a Chinese ship to unload arms headed for the landlocked country.
The United States has led international calls for Africa to do more to end the Zimbabwe crisis. Washington's chief Africa diplomat, Assistant Secretary of State Jendayi Frazer, was due in South Africa on a previously-arranged regional tour.
Archbishop Makgoba, in a clear reference to President Thabo Mbeki's softly softly approach to Zimbabwe, said South Africa's leaders appeared to many outside the country to be "heartless and unmoved by the suffering of Zimbabweans".
