Harare  - Zimbabwe's election chief says he will announce by Saturday the date for the controversial run-off presidential election pitting President Robert Mugabe against opposition leader Morgan Tsvangirai, state media reported Friday.

"The electorate is eagerly waiting to hear the date of the run- off," Judge George Chiweshe, chairman of the state-controlled Zimbabwe Electoral Commission, said in an interview with the daily Herald newspaper.

"The commission will issue an instrument (official notification) in the next 48 hours indicating when the run-off will be held," he added.

Mugabe, 84, leader since independence in 1980 and accused of gross human rights violations, and former national trade union leader Tsvangirai are due to square off again after neither achieved over 50 per cent of the vote needed for outright victory in the March 29 elections.

After a five-week delay in the announcement of the presidential result, Tsvangirai was given 47.9 per cent of the ballot, to 43.2 per cent for Mugabe.

Human rights organisations, churches and diplomats report that ruling party militias are carrying out a nationwide campaign of vengeance attacks on supporters of Tsvangirai's Movement for Democratic Change for voting for the opposition in March, and to terrorise them into voting for Mugabe in the run-off.

Rights groups say 40 people have been killed and 1,000 have had to be treated in hospital for severe injuries incurred during beatings that there were probably twice as many victims not yet known about, who were too frightened to present themselves to health centres.

On Wednesday the government announced that it had extended from 21 to 90 days the period within which the run-off can be held following the initial announcement of the election result.

"First they withheld the election result, then they had an illegal recount (of the parliamentary election results in which the MDC won an overall majority)," MDC spokesman Nelson Chamisa said.

"Now they are talking about a 90-day extension. This is going to be 90 days of beating of the people, killing and destroying property," he charged. (dpa)