Zimbabwe began a partial recount of votes from the March 29 elections on Saturday, despite opposition efforts to block it and widespread fears that political stalemate could erupt into violence.

The recount in 23 of 210 constituencies could overturn the results of the parliamentary election, which showed President Robert Mugabe's ruling ZANU-PF losing its majority to the opposition Movement for Democratic Change for the first time.

ZANU-PF lost 16 out of those 23 constituencies in the original count, the Zimbabwe Electoral Commission said. The ruling party needs to win 9 seats to get a simple majority in parliament. Results of a parallel presidential vote have not been released, but MDC leader Morgan Tsvangirai says he has won.

"The vote recounting process has started, and it's going to be a thorough exercise. We expect it to take about three days," a Zimbabwe Electoral Commission official told Reuters.

Tsvangirai says the recount is illegal, and the MDC said it would not accept its outcome. There have been concerns in the West and among the MDC that Mugabe is trying to rig the results.

"We reject the process. We reject the outcome of this flawed process," MDC spokesman Nelson Chamisa told Reuters. "As far as the MDC is concerned, the first results stand. Anything else will be an illegitimate process."

A South African-led team from the 14-nation Southern African Development Community (SADC) is observing the recount.

Both U.S. President George W. Bush and Secretary of State Condoleezza Rice have urged African states to take more action to end the post-election deadlock in Zimbabwe.

SADC last weekend called for the outcome to be announced quickly, but African reaction has been muted overall. The continent has largely taken its cue from South African President Thabo Mbeki, attacked both at home and abroad for his "quiet diplomacy" approach to Mugabe.

A Reuters correspondent at one of the counting stations - in Domboshava rural district about 30 km (20 miles) north of Harare - said SADC observers and diplomats were present to witness the vote recount.

DISPUTED ELECTION

It is unclear when results of the recount, which includes votes cast in the presidential election, will be issued.

Police spokesman Wayne Bvudzijena told the state-controlled Herald newspaper petrol bombs were thrown at offices where ballot boxes for three constituencies in the Gutu rural district were stored early Friday morning, but all failed to explode.

ZANU-PF triggered the recount after it formally accused election officials of taking bribes to undercount votes for Mugabe and his ruling party and committing other electoral fraud. A number of election officials have been arrested since.

Harare's High Court rejected an MDC bid to block the recount on Friday. The court had previously denied its request to force authorities to release the result of the presidential vote.

Opponents accuse the 84-year-old Mugabe of wrecking this once-prosperous country, where the collapse of the economy and inflation of about 165,000 percent have led to chronic shortages of water, food and fuel, and 80 percent unemployment.

The delay in announcing results has given rise to opposition fears the recount could be a government ploy to steal the election.

"Clearly these guys have tampered with the boxes. They can't deny that," the MDC's Chamisa said. "How do you expect us to have confidence in the process?"

He said that in the Mberengwa West constituency, for example, the recount had been halted and paperwork including a copy of the voter roll were missing from the ballot box. He said some boxes from the Silobela constituency were not sealed.

Mugabe, in power since independence from Britain in 1980, has brushed aside criticism from London, Washington and opponents at home and is preparing for an expected run-off against Tsvangirai.

The MDC has accused the former guerrilla commander of unleashing loyal militias to help him rig victory in the runoff and allowing veterans of the independence war to invade some farms, echoing a wave of land invasions that began in 2000.

Human Rights Watch said on Saturday that ZANU-PF was using a network of informal detention centres to beat, torture, and intimidate opposition activists and ordinary Zimbabweans into voting for the ruling party.

On Friday, Mugabe said his government was only interested in peace and had intervened to stop war veterans from taking up arms.