Zimbabwe's rival presidential candidates both claimed on Tuesday they were heading for election victory, setting up a tense count in the country's first vote since the ouster of longtime ruler Robert Mugabe.President Emmerson Mnangagwa said his ruling Zanu-PF party was receiving "extremely positive" data, while opposition leader Nelson Chamisa said the MDC party was "winning resoundingly".The claims pointed to a contested result in the historic election, raising the prospect of competing fraud allegations and a possible run-off vote in September - required if no candidate wins at least 50% of ballots in the first round.Zanu-PF has held an iron grip on power in Zimbabwe since independence from British colonial rule in 1980, and victory for the opposition would be a major upset.Analysts have said it was unclear whether the country's military generals, who ousted Mugabe and ushered Mnangagwa to office last year, would accept a win by the Movement for Democratic Change.Defeat for the ruling party would likely lead "to a denunciation of the election by the Mnangagwa administration and the potential for the military to intervene to secure power for Zanu-PF," the London-based BMI risk consultancy said. Anxious wait for results "I am scared - is there going to be unrest?" Stone Sibanda, a 39-year-old taxi driver in Harare, told AFP. "It is a very sensitive moment. Everyone is anxious.Estimated turnout was around 75% before polls closed on Monday evening after a peaceful day of voting.Early results from the elections - presidential, parliamentary and local - are expected Tuesday, and full results are due by Saturday.At one polling station in the capital Harare, officials counted large piles of ballots using gas lanterns and candles late into the night on Monday.If required, Zimbabwe's 5.6 million registered voters would be asked to return to the polls to vote in a presidential run-off on September 8.But Mnangagwa, 75, Mugabe's former right-hand man, was confident of an outright first-round win."The information from our reps on the ground is extremely positive! Waiting patiently for official results as per the constitution," Mnangagwa said on Twitter.Chamisa, 40, who raised allegations of voter fraud repeatedly during the campaign, was equally buoyant, saying that his MDC was ready to form the next government."Winning resoundingly... We've done exceedingly well," he said on Twitter.Zimbabwe's much-criticised election authority declared on Tuesday that the vote had been free of rigging - even though the count was not yet completed."We are absolutely confident there was no rigging... we at the Zimbabwean Election Commission will not steal (the people's) choice of leaders, we will not subvert their will," said ZEC chair Priscilla Chigumba.Mugabe, 94, whose authoritarian 37-year regime held power through violent, fraud-riddled elections, voted in Harare alongside his wife Grace after a surprise press conference at his home on Sunday at which he called for voters to reject Zanu-PF.EU cites 'shortcomings' Once-banned European Union election observers, present for the first time in years, said participation appeared high but warned of possible problems in the polling process."There are shortcomings that we have to check. We don't know yet whether it was a pattern or whether it was a question of bad organisation in certain polling stations," the EU's chief observer Elmar Brok told AFP on Monday.The bloc will deliver a preliminary report on the conduct of the election on Wednesday, as will the Southern African Development Community (SADC) and the African Union teams.Mnangagwa was the clear election front-runner, benefitting from tacit military support, loyal state media and ruling party controls of government resources.But Chamisa, a young lawyer and pastor who performed strongly on the campaign trail, sought to tap into the huge youth vote.The new government must tackle mass unemployment and an economy shattered by the seizure of white-owned farms under Mugabe, the collapse of agriculture, hyperinflation and an investment exodus.Previously solid health and education services are in ruins, and millions have fled abroad to seek work.Both candidates had vowed to clean up government and attract foreign investment to create jobs after the isolation and systematic corruption of the Mugabe era.In 2008, then opposition leader Morgan Tsvangirai pulled out of the presidential run-off against Mugabe after attacks orchestrated by the state claimed the lives of at least 200 of his supporters.* To follow the latest on the Zimbabwe elections SIGN UP TO THE HELLO AFRICA NEWSLETTERFOLLOW News24 Africa on Twitter and Facebook.