Zimbabwe votes: Tsvangirai challenges Mugabe in critical election (VIDEO)

The polls have closed in Zimbabwe after the public voted in elections that will decide who leads the country for the next five years.

The African Union's election observer chief said initial reports suggested the elections were peaceful, orderly, free and fair. No Western observers were allowed to monitor the voting.

Opposition leader Morgan Tsvangirai is running against Robert Mugabe for the presidency in what is expected to be the most serious challenge the long-time ruler has yet faced in all his 33 years in power. The election will also determine the next parliament.

Polls opened at 7 a.m. local time, with a long queues reported outside. By 2 p.m., African Union observers said that voting was "proceeding in an orderly and peaceful manner."

Polling stations were due to close at 7 p.m. local time, but because of high voter turnout, election officials said those waiting in line would be allowed to vote until midnight.

BBC's Africa correspondent Andrew Harding tweeted about alleged vote rigging and the discovery of a fake polling station.

Mugabe, 89, has promised not to cling to power if he loses the election. Yet his opponents claim that he and his Zanu-PF party are taking steps to ensure that doesn't happen. 

"He does not believe in the right of the people to choose," Tsvangirai, who serves as Mugabe's prime minister under a 2009 power-sharing agreement, told the BBC. "He does not believe he can be voted out of office."

Tsvangirai's Movement for Democratic Change (MDC) has accused Zanu-PF of adding thousands of invalid names to the electoral roll, which was released just a day before voting began. 

The MDC was also advising its supporters to use their own pens to fill out voting slips.

Mugabe refutes all allegations of irregularities, and said as he cast his vote: "I am sure people will vote freely and fairly, there is no pressure being exerted on anyone."

Despite the controversy, Tsvangirai predicted that his party would win "quite resoundingly."

"This is a very historic moment for all of us," Tsvangirai told reporters as he voted in the capital, Harare. "Finally Zimbabwe will be able to move on again."

Results are expected to be announced by Aug. 5. If no candidate wins more than 50 percent of the vote, the presidential contest will go to a run-off in September.

The AP posted video of the main two candidates posting their ballots: