This week's election in Zimbabwe was "seriously compromised" with up to a million people prevented from voting, the largest observers' group has said.
Most of those turned away were in urban areas, where support for Prime Minister Morgan Tsvangirai is strong, said the Zimbabwe Election Support Network.
It noted that fewer voters were rejected in rural areas, seen as strongholds of President Robert Mugabe.
Mr Mugabe's allies are already claiming a victory in Wednesday's poll.
"We've buried the MDC [Mr Tsvangirai's Movement for Democratic Change]," a senior party source told Reuters news agency.
It is illegal to publish unofficial results.