Hospitals are said to be struggling to cope with the injured
Opposition leader Morgan Tsvangirai has said he will win Zimbabwe's 27 June run-off presidential poll, as he returned to Harare after weeks abroad.
The Movement for Democratic Change leader accused the ruling Zanu-PF party of seeking to "decimate" opposition structures ahead of the vote.
His first engagement was to visit supporters hurt in political violence.
Mr Tsvangirai's return was delayed amid an alleged army plot to kill him, which the ruling party said was "fantasy".
Polls on 29 March saw the country's veteran leader, Robert Mugabe, lose his parliamentary majority for the first time in two decades in power.
The MDC leader says he gained the more than 50% of the presidential vote needed to win without a run-off, but official results - released after long delays - said he gained 47.9%, with Mr Mugabe taking 43.2%.
Morgan Tsvangirai on the forthcoming presidential run-off
Mr Tsvangirai said the Southern African Development Community (Sadc) would meet on Tuesday to discuss the possible deployment of peacekeepers and election monitors, amid fears that a Zanu-PF campaign of intimidation is making a fair second round impossible.
He said they would be of little use if not in place by 1 June.
He said he had been impressed by the supporters he met in hospital, and that he would win the run-off election.
"I saw people with scars and bruises. They said 'president, we will finish him off on June 27'."
"If Mugabe thinks he has beaten people into submission, then he will have a rude shock on the 27 of June," he said.
Mr Tsvangirai also said the recent deaths of more than 40 people - many of them Zimbabwean - in anti-immigrant violence in South Africa could be "directly attributed" to "Mugabe's failed policies of intolerance and repression".
There are believed to be between three and five million foreigners living in South Africa, most of them Zimbabweans fleeing poverty and violence at home.
Correspondents say Mr Tsvangirai has been criticised for spending the last seven weeks abroad while hundreds of his supporters have been beaten up and at least 40 killed, according to human rights and opposition groups.
Hospitals have been struggling to cope with admissions, the BBC's Peter Biles in Johannesburg says, as a result of what is widely perceived to be a government campaign of intimidation against MDC supporters.
ZIMBABWE ELECTIONS TIMELINE
29 March: Elections mean Zanu-PF party loses majority for the first time since independence in 1980
19 April: Election officials begin recounting votes cast in the disputed polls
3 May: Official results of presidential election show Morgan Tsvangirai won but fell short of the 50% needed to win completely.
17 May: MDC alleges military plot to assassinate Morgan Tsvangirai
President Mugabe's ruling Zanu-PF party denies supporting violence and says the West is trying to demonise Zimbabwe.
Last year, Mr Tsvangirai was treated in hospital after being assaulted by police. He has also been arrested several times and accused of treason.
Mr Mugabe has accused the MDC of fomenting violence since the disputed first round election.
The BBC's Will Ross in Johannesburg says voting in the first round was fairly free and fair by Zimbabwean standards.
But, he says, it is not clear whether Robert Mugabe will risk allowing the second round to be free and fair, because that could see him being trounced as Zimbabwe's worsening economic situation is turning voters against him.
Mr Tsvangirai has spent nearly two months abroad, mainly in South Africa, trying to drum up international support.
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