Harare  - The day after Zimbabwe's election commission announced presidential poll results indicating a runoff election was needed, President Robert Mugabe's party said Saturday it was launching a legal challenge to 52 parliamentary seats won by the opposition Movement for Democratic Change (MDC).

ZANU-PF chief election agent Emmerson Mnangagwa was quoted by the state-run daily The Herald as saying the ruling party candidates had filed petitions to this effect in the Electoral Court.

"The party's candidates have filed petitions in 52 constituencies seeking the setting aside of the announced results and these petitions have been filed with the Electoral Court," he said.

The MDC has already said that, for its part, it is challenging 60 seats won by Zanu PF. in the March 29 parliamentary elections held at the same time as the presidential poll, in which the MDC won 99 seats, its splinter won 10, and ZANU-PF won 97.

Presidential results released Friday by the country electoral commission showed there was no outright winner, thus pitting Mugabe and the MDC's Morgan Tsvangirai for a run-off within 21 days under Zimbabwe's electoral laws.

However, opposition leaders denounced government demands for a run-off election as "grand theft" and insisted they had won the elections.

They said late Friday they would decide over the weekend whether to participate in another round of voting.

This was stated late Friday by Tendai Biti, Secretary General of the Movement for Democratic Change, in South Africa - where many MDC supporters have fled seeking refuge from violent attacks by Mugabe's supporters since the elections.

Biti also suggested that Mugabe be given a figurehead position in a new "government of national healing" which would be headed by Tsvangirai.

Zimbabwe's Election Commission (ZEC) said Friday the long-delayed results showed Tsvangirai was the top vote-getter with 47.9 per cent, beating Mugabe's 43.2 per cent.

Mugabe has been president for nearly three decades. The results marked the first time in several controversial elections that the official election organization conceded more votes to a Mugabe challenger.

But the MDC insists it won the 50 per cent required for an outright win. Biti charged that the commission used the month-long delay to manipulate almost 90,000 votes by adding more than 37,000 votes to Mugabe and removing 50,000 votes from Tsvangirai.

Under pressure from his own party, religious leaders and the international community, South African President Thabo Mbeki - who has insisted Zimbabwe's elections were an internal matter - signalled late Friday that he would immediately send a team to Zimbabwe to investigate reports of violence against opposition supporters.

"He assured us that he would do everything to ensure that the run- off election happens in an atmosphere of peace," said Reverend Nyansako-ni-Nku, president of the All Africa Conference of Churches.

The minister spoke to reporters after four hours of talks between religious leaders and Mbeki at the presidential guesthouse in Pretoria, SAPA news agency reported.

"The president said that right away they will dispatch a team to check every allegation of violence," the minister said. Mbeki did not speak directly to reporters.

In Harare, the regional group, Southern African Development Community, said it found an increase in violence and a "tense environment" amidst "inflammatory utterances" by both ruling party and opposition leaders during the election recount.

Jose Marcos Barrica, Angola's minister of youth and sport who is heading the SADC mission, noted that torture, killings and destruction of goods had taken place in a "climate of political intolerance" that he blamed on "leaders who took part in the elections."

The British and US governments said the results announced Friday lacked "credibility." A runoff would "not be fair unless international monitors were present," Britain's Foreign Office said.

In Washington, US State Department deputy spokesman Tom Casey called for Mugabe's government to "cease the kinds of action it's been taking against the opposition before anyone should even think" about a run-off.

The MDC Friday estimated that 20 opposition supporters have been killed by Mugabe's strike troops. Human Rights Watch accused Zimbabwe's military of participating in the attacks.

In South Africa, the chairman of the ruling African National Congress party (ANC) Jacob Zuma again distanced himself from Mugabe's policies.

The South African leader announced measures to limit the illegal entry into South Africa of Zimbabweans, whose numbers are estimated at up to 3 million.

Lawyers for Human Rights, a rights activist group, reported 150 teachers had been arrested for allegedly favouring the opposition in their role as election monitors.

Late Friday, a Zimbabwe High Court judge granted bail to 50 members of the opposition and a freelance journalist arrested two weeks ago after the opposition called for a nationwide strike to press for release of the election results.

The ruling overturned a lower court insistence that they not be released because of the country's "volatile" situation.

The released journalist, Frank Chikowore, was arrested on April 15 as he was covering the strike. (dpa)