Harare (AFP) - Zimbabwe's opposition MDC party on Tuesday claimed victory in the country's historic elections while the government threatened to jail leaders announcing results as the wait for official tallies dragged on.

Electoral officials warned that gathering the results of the poll, which President Emmerson Mnangagwa said looked "extremely positive" for him, was "nowhere near" complete and no announcement would be made until as late as Saturday.

The candidates' competing claims following the first elections since former leader Robert Mugabe was ousted in November raise the prospect of fraud allegations and a possible run-off vote on September 8.

That would be required if no candidate wins 50 percent of ballots cast by Zimbabwe's 5.6 million voters in the first round.

Opposition Movement for Democratic Change (MDC) official Tendai Biti said on Tuesday that the party was sure its candidate Nelson Chamisa had won and that if he was not declared victorious, it would "announce our own results".

That apparently prompted Home Affairs Minister Obert Mpofu to warn that anyone doing so would "provoke the wrath of the law and risk being sent to jail".

"We have noted with concern the actions and conduct of some political party leaders... who are openly declaring that they will announce results irrespective of provisions of the law," Mpofu said at a media briefing in harare. It is illegal to announce results before the Zimbabwe Electoral Commission (ZEC).

The commission had earlier warned that the results of the presidential first round may not be known until Friday or even Saturday and would not be released until tallies were received from all 10,985 polling stations.

"We are nowhere near where we expected to be, so I can quite see us going into the fifth day which is allowed by law -- but we are working flat-out," ZEC chairwoman Priscilla Chigumba told journalists in the capital.

On Wednesday attention will shift to the European Union's electoral monitoring team which will deliver a much-anticipated report on the conduct of the campaign, the polls and counting processes.

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Their findings will also be an important verdict on Mnangagwa, 75, who has staked his reputation on delivering credible polls.

"There are shortcomings that we have to check. We don't know yet whether it was a pattern," the EU's chief observer Elmar Brok told AFP during voting Monday.

Observers from the Southern African Development Community (SADC) and the African Union will also deliver reports on the polls.

- 'Deliberate delay' -

Biti had earlier accused the ZEC of deliberately delaying the publication of results to help Mnangagwa's ruling ZANU-PF party.

"The results show beyond reasonable doubt that we have won the election and that the next president of Zimbabwe is Nelson Chamisa," Biti told a press conference at the party's headquarters in Harare on Tuesday.

Outside, MDC supporters danced jubilantly in the street brandishing "Vote Nelson Chamisa" posters while four water cannons and police personnel carriers patrolled nearby.

"We are however seriously concerned about evidence of interference... there is a deliberate delay in announcing the results. This delay is totally unacceptable," Biti added.

ZEC chair Chigumba has flatly denied allegations of bias and strongly disputed accusations of rigging.

Analysts have said it was unclear whether the country's generals, who ousted Mugabe and ushered Mnangagwa into office, would accept an MDC victory.

- Military intervention? -

"There is no way that ZANU-PF will accept an MDC victory. We know that people will be beaten -- especially in rural areas, like what they were doing before," said Harare shop worker Tracy Kubara, 26.

Ninety-four-year-old Mugabe, who was accused of political violence and rigging elections during his nearly four decades in power, voted in Harare alongside his wife Grace.

It followed a surprise press conference at his home on Sunday at which he stunned observers and called for voters to reject ZANU-PF, his former party.

Mnangagwa, Mugabe's former right-hand man, was the clear election front-runner, benefitting from tacit military support and control of state resources.

But Chamisa, 40, a lawyer and pastor who performed strongly on the campaign trail, sought to tap into the youth and urban vote.

He has repeatedly accused ZANU-PF and election authorities of trying to use a flawed electoral register and fixed ballot papers to steal the election.

Whoever wins will face a mass unemployment crisis and an economy shattered by the Mugabe-era seizure of white-owned farms, the collapse of agriculture, hyperinflation and an exodus of investment.