Long queues have formed at polling stations in Zimbabwe as people vote in fiercely contested elections which have already been hit by fraud allegations.
President Robert Mugabe, 89, has said he will step down after 33 years in power if he and his Zanu-PF party lose.
Prime Minister Morgan Tsvangirai's Movement for Democratic Change (MDC) have accused Zanu-PF of doctoring the electoral roll, a charge it has denied.
Campaigning for the presidential and parliamentary poll was mostly peaceful.
Zanu-PF and the MDC have shared an uneasy coalition government since 2009 under a deal brokered to end the deadly violence that erupted after a disputed presidential poll the previous year.'Determined to vote'
"They want to find a way out," Mr Mugabe said.Mr Mugabe dismissed the MDC's allegations of vote-rigging as "politicking" as he voted in the capital Harare's Highfield township, AFP news agency reports.
"I am sure people will vote freely and fairly, there is no pressure being exerted on anyone."
Mr Tsvangirai described casting his ballot as an emotional moment "after all the conflict, the stalemate, the suspicion, the hostility".
"This is a very historic moment for us," he is quoted by AFP as saying.
Mr Tsvangirai won the most votes in the first round of the 2008 poll, but pulled out of the run-off with Mr Mugabe because of attacks on his supporters.
The government has barred Western observers from monitoring Wednesday's elections, but the African Union (AU) and the Southern African Development Community (Sadc), as well as local organisations, have been accredited.
Polls opened at 07:00 local time (05:00 GMT) and are due to close at 17:00 GMT.
The turnout is expected to be high among the 6.4 million people registered to vote, with tens of thousands attending rallies in recent weeks. Results are expected within five days.
Wednesday has been declared a national holiday to ensure people can vote. Despite this, voters queued for several hours outside polling stations across the country before they opened, reports the BBC's Nomsa Maseko in Harare.
Zimbabwe Election Support Network, the main domestic monitoring agency, said the vote appeared to be taking place without too many problems, Reuters news agency reports.
"There are some concerns around long queues, but generally, it's smooth," said its spokesman Thabani Nyoni.
"I got up at four but still couldn't get the first position in the line," Clifford Chasakara, a voter in the western province of Manicaland, told the Reuters.
"My fingers are numb, but I'm sure I can mark the ballot all the same. I'm determined to vote and have my vote counted."
Mr Tsvangirai, who voted in Harare's middle class suburb of Mt. Pleasant, said there was a sense that "finally Zimbabwe will be able to move on again", AFP reports.
His party will win "quite resoundingly, I must say", he added.
At a news conference at State House on Tuesday, Mr Mugabe was asked if he and Zanu-PF would accept defeat.
"If you go into a process and join a competition where there are only two outcomes, win or lose, you can't be both. You either win or lose. If you lose, you must surrender," he said.
But Mr Tsvangirai dismissed the president's remarks.
"He does not believe in the right of the people to choose. He does not believe he can be voted out of office," he told the BBC.
The 61-year-old has vowed to push Mr Mugabe into retirement; it is his third attempt to unseat him.
An MDC spokesman said separately that the party was only prepared to accept the results of the elections if they were "free and fair".