Zimbabwe's opposition has accused the election commission of deliberately delaying results of this week's vote to favour the ruling party, reporting irregularities in the first poll since the removal of Robert Mugabe as president in November.

Even though the election passed off peacefully, several water cannon trucks patrolled outside the central Harare headquarters of the opposition Movement for Democratic Change (MDC) as its red-shirted supporters danced in the streets.

Some local results from parallel parliamentary elections have been declared but the Zimbabwe Electoral Commission (ZEC) has yet to produce any figures from yesterday's presidential vote.

ZEC chief Priscilla Chigumba said the presidential result may not be ready until Saturday 4 August.

Former MDC finance minister Tendai Biti and ZESN, the main domestic election monitor, said one in five polling stations - more than 2,000 in all - had not physically posted tallies on their doors, as required by law.

That omission gave room for the ZEC, which ZESN and the opposition have accused of bias, to manipulate the results in favour of President Emmerson Mnangagwa and the ruling ZANU-PF party, Mr Biti said.

"There is a deliberate delay in formally announcing results," Mr Biti told a news conference, characterising it as "interference with the people's will".

ZESN and other civil society groups were preparing a legal challenge to force the results into the open, Mr Biti said.

ZEC said there was no rigging or cheating in the vote, whose credibility is vital in Zimbabwe's attempts to emerge from the pariah status and economic decay into which it sank in the latter half of Mr Mugabe's nearly four decades in charge.

However, ZEC did not explain the failure by the polling stations to post results.

The poll is a two-horse race between 75-year-old Mr Mnangagwa, a long-serving security chief who took over after Mr Mugabe's removal, and 40-year-old MDC leader Nelson Chamisa.

Both men have expressed confidence in victory although western diplomats and local observer groups said the race, which saw a turnout of 75%, was too close to call.

Candidates Emmerson Mnangagwa (left) and Nelson Chamisa

"The information from our representatives on the ground is extremely positive!" Mr Mnangagwa said on his official Twitter feed.

Mr Chamisa had earlier said he was poised for victory, writing on Twitter: "Awaiting ZEC to perform their constitutional duty to officially announce the people's election results and we are ready to form the next government."

As well as electing a president, Zimbabweans were voting for 210 members of parliament and more than 9,000 councillors.

The final outcome may not be known until Saturday.

In the absence of a clear winner, a run-off will be held on 8 September.

The winner must put Zimbabwe back on track after 37 years under Mr Mugabe tainted by corruption, mismanagement and diplomatic isolation that brought one of Africa's most promising economies to its knees.

Election monitor sources said yesterday's vote appeared to have passed without major foul play although they noted some coercion and intimidation of voters in rural areas by ZANU-PF and said state media was biased towards the ruling party.