Hospitals are said to be struggling to cope with the injured
Zimbabwe's opposition leader Morgan Tsvangirai has returned to Harare to begin his presidential election run-off campaign, after spending weeks abroad.
The Movement for Democratic Change leader's first engagement was to visit supporters hurt in political violence.
Mr Tsvangirai said they had vowed to "finish off" President Robert Mugabe in the 27 June second round vote.
Mr Tsvangirai's return was delayed amid an alleged army plan to kill him, which the ruling party said was "fantasy".
Mr Tsvangirai said the South African Development Community (Sadc) would meet on Tuesday to discuss the possible deployment of peacekeepers and election monitors, amid fears that election violence 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'."
Opposition and human rights groups have said hundreds of opposition supporters have been beaten up and at least 40 killed since the first round on 29 March.
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
24 May: Morgan Tsvangirai returns to Zimbabwe
27 June: Scheduled presidential election run-off
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.
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.
Mr Tsvangirai has spent nearly two months outside Zimbabwe, mainly in South Africa, since the first round trying to drum up international support.
According to official results, the MDC leader won the presidential poll, but not by enough to avoid a run-off with President Mugabe.
The Zimbabwe Electoral Commission said Mr Tsvangirai won 47.9% of the vote, with Mr Mugabe taking 43.2%.