Biti, speaking after a meeting with the electoral commission, added: “They are admitting that there’s still two million people who are dead on the voters’ roll, but they said ‘because they’re dead, they can’t vote’.”
The MDC has handed its evidence to observers from the Southern African Development Community (SADC).
Since no Western groups were allowed to cover the presidential and parliamentary poll, the SADC’s account will be closely watched.
The African Union, which has been accused of whitewashing problems in the run up to the vote, said initial reports indicated it was “peaceful, orderly, free and fair”.
In Washington, US State Department spokeswoman Marie Harf also said that early signs indicated a “peaceful environment” — but that it was too soon to say if the election had been fair.
“We’ve made clear to the government of Zimbabwe and the region that further reductions in our sanctions will only occur if these next elections are credible, transparent and reflect the will of the Zimbabwean people,” she told reporters.
Tsvangirai cut a confident figure as he cast his own ballot, predicting his MDC would win “quite resoundingly”.
“This is a very historic moment for all of us,” he said. It is the time to “complete the change”.
Turnout appeared to be particularly brisk in the urban areas where Tsvangirai has enjoyed his strongest support, and which he must retain to stand any chance of victory.
But some analysts cautioned against interpreting the high urban turnout as a sign Tsvangirai would sweep the election.
“This election is going to be decided in the rural areas,” where two thirds of Zimbabweans live and where Mugabe enjoys strong support, said Michael Bratton, founder of polling organisation Afrobarometer.
Police warned on Wednesday that anyone trying to release unofficial results ahead of the official figures risked being arrested.
Already Sunday, Mugabe had threatened to arrest Tsvangirai if he tried to declare an early victory.
Some 6.4 million people, around half of the population, are eligible to vote. A candidate needs 50 percent of the vote to avoid a run-off.
The sharp-tongued Mugabe has focused his campaign on attacking homosexuals and on promises to widen the redistribution of wealth to poor black Zimbabweans.
As the economy recovers from a crisis that saw mass unemployment and galloping inflation, Mugabe loyalists insist their hero is “tried and tested”.
Tsvangirai hopes his plans to lure back foreign investors, create a million jobs in five years and improve public services will deliver a long-awaited victory.
The final results are expected within five days.