Tsvangirai rejects 'sham' ballot
Morgan Tsvangirai has described Zimbabwe's election run-off as "an excercise in mass intimidation".
Mr Tsvangirai, who boycotted the poll because of violence, said people across Zimbabwe had been forced to take part and urged the world to reject the vote.
The European Union and the US dismissed the vote as meaningless.
Turnout is reported to have been low. President Robert Mugabe - the only candidate - is assured of victory.
Official results are expected at the weekend.
The Zimbabwe Election Support Network, a monitoring group, reported that people had been forced to vote in most rural areas.
A Zimbabwean journalist said militias loyal to Mr Mugabe had gone door-to-door in townships outside the capital, Harare, to coerce people.
Apparently barely anyone turned out to vote.
"We saw one long queue, which we mistook for a polling station, only to find the people were queuing for bread," he said, adding that the ingredients for a free and fair election were missing.
But Justice Minister Patrick Chinamasa told the BBC that people were aiming to preserve Zimbabwe's independence.
"They are voting to say no to the recolonisation of our country," he said.
As he cast his vote in Harare, Mr Mugabe, who is 84, said he was feeling "very fit, very optimistic".
The BBC's reporter in Zimbabwe, John Simpson, said that this is the most frightening election he has ever seen.
He adds that if someone summoned up the courage to vote for Mr Tsvangirai - whose name is still on the ballot - there were fears their identity could be discovered.
Mr. Tsvangirai spoke out agains the election earlier:
He called the poll a "sham" exercise staged by a "dictatorship desperate for the illusion of legitimacy".
Mr Tsvangirai also urged the international community to reject the results.
"Anyone who recognises the result of this election is denying the will of the Zimbabwean people," he said.
The MDC leader has been taking refuge at the Dutch embassy for most of the past six days.
Mr Mugabe came second to Mr Tsvangirai in the first round of the presidential vote in March.
Since then, the MDC says some 86 of its supporters have been killed and 200,000 forced from their homes by militias loyal to Zanu-PF.