Zimbabwe's election took an uneasy turn Tuesday when the opposition alleged results were not posted outside one-fifth of polling stations, as required by law, and the electoral commission said the already-impatient nation would have to wait longer to learn who will be its next president.

The government of incumbent President Emmerson Mnangagwa, meanwhile, suggested the main opposition leader, Nelson Chamisa, and his supporters were inciting "violence" by declaring he had won Monday's election even though only a few parliamentary returns have been announced.

"Let me also warn such individuals and groups that no one is above the law," Home Affairs Minister Obert Mpofu said. Security forces "will remain on high alert and continue to monitor the security situation in the country."

Zimbabweans went to the polls on Monday to elect three layers of leadership: 210 members of parliament, more than 9,000 ward councillors and their nation's president. It was the first general election since former president Robert Mugabe was forced to resign in November after Zimbabwe's military and ruling ZANU-PF party turned on him. The 94-year-old ex-leader had been in power since 1980.

Some local results have been announced, but the presidential tallies are under wraps until all ballots are counted. The Zimbabwe Electoral Commission has five days from the end of voting to release the final tally.

Police water cannons are seen in the capital, Harare, Tuesday. (Tsvangirayi Mukwazhi/Associated Press)

Mnangagwa, the 75-year-old former deputy president, has said his showing in the presidential polls was "extremely positive" while urging people to wait for official results.

Chamisa, a lawyer and pastor who leads the opposition Movement for Democratic Change party, has gone further, saying his own count shows he won the election and that he's ready to form the next government.

Chamisa's party also said results have not been posted outside 21 per cent of the country's nearly 11,000 polling stations, raising concerns about possible vote-rigging. It suggested there was a deliberate effort to delay announcing the results, reflecting deep suspicion about the panel presiding over the election.

'Peaceful' atmosphere

Priscilla Chigumba, a judge who heads the Zimbabwe Electoral Commission, said she was confident there had been no "cheating" in the first election without Mugabe on the ballot. Each polling station must post its results outside after vote-counting, she said.

"We will not steal their choice of leaders, we will not subvert their will," Chigumba said.

"The atmosphere has remained peaceful" and the commission has not received any major complaints about the election, she said.

If no presidential candidate wins more than 50 per cent of the vote, a runoff will be held Sept. 8.

Vote counting at a polling station in Bulawayo, Zimbabwe, on Monday. The historic election is the first since the fall of longtime leader Robert Mugabe. (Jerome Delay/Associated Press)

More than 5.5 million people were registered to vote in an election featuring a record number of more than 20 presidential candidates and nearly 130 political parties.

Western election observers were in Zimbabwe, a sign of a freer political environment since the resignation of Mugabe, who declared he would not vote for the ruling party he long controlled and called​ Chamisa the only viable candidate.

Meanwhile, a monitoring group, the Zimbabwe Election Support Network, issued preliminary findings on the vote, noting improvements such as a biometric registration system that reduced the chances of fraud.

However, it noted problems with implementation, saying the election commission at one point allotted more registration kits to rural areas and fewer to urban areas. The ruling party has strong rural support, while the opposition is popular in the cities.

Monitors report 'inconsistencies'

Elmar Brok, head of the European Union monitoring mission, said Tuesday that his team had noted some "inconsistencies," but overall, there was "progress" compared to past elections.

Under Mugabe, elections were often marred by violence, harassment and irregularities.

"In African elections, often stakes are very high and nobody has a backup plan for losing," said John Dramani Mahama, former president of Ghana and head of the observer mission from the Commonwealth group of nations, mostly former British colonies.

Mnangagwa leaves the polling station after casting his vote at the Sherwood Primary School in Kwekwe. Once Mugabe's deputy, Mnangagwa positioned himself as a candidate for change. (Jerome Delay/Associated Press)

The contenders in Zimbabwe's vote must accept the results and "should look at the larger picture of success — a successful election for Zimbabwe," he said.

Zimbabwe and the Commonwealth split in the early 2000s over the group's concerns about election-related violence and intimidation in the southern African nation. Under Mnangagwa, Zimbabwe has said it wants to rejoin the group.

A voter in Harare, the capital, said Zimbabwe is anxious to hear the election results as soon as possible.

"I think the best thing is they got to announce the results as early as possible so that everyone will be settled," said 65-year-old voter Chaka Nyuka in the capital of Harare. "Because people are not yet settled, they're thinking of too many things. They need a good change. People are looking for that."