Zimbabwean President Robert Mugabe is accusing the opposition of embarking on what he calls "an evil crusade" to divide the country.
Mr. Mugabe Wednesday blamed the Movement for Democratic Change for the wave of violence that has swept across the country since disputed March elections.
But the MDC says militias loyal to Mr. Mugabe have been methodically intimidating and attacking opposition activists. The party says 43 opposition supporters have been killed by Mugabe loyalists.
The violence erupted after Zimbabwe's electoral commission announced earlier this month that opposition leader Morgan Tsvangirai had beaten Mr. Mugabe in the presidential race, but did not win enough votes to avoid a runoff election.
The state-run Herald newspaper says Mr. Mugabe will officially launch his runoff election campaign on Sunday.
In a report Tuesday, the International Crisis Group said it will be impossible to hold a credible runoff election because of the violence and intimidation carried out by the ruling party.
The group said Mr. Tsvangirai has won the right to head a coalition government. It urged African leaders to intervene in Zimbabwe's crisis, stressing that continued rule by President Mugabe would have disastrous results for the nation.
Also Tuesday, Zimbabwe's opposition questioned the credibility of a joint-committee set up by the Mugabe government to investigate election-related violence.
The opposition said the government set up the committee to deflect international attention from its crimes.