Morgan Tsvangirai, the leader of Zimbabwe's Movement for Democratic Change (MDC), said he totally rejects the result of the election.
He claimed there is evidence to show that his party won the election and it will exhaust all legal remedies to challenge the result.
Zimbabwe's President Robert Mugabe could be in power for forty years, if he claims victory in Wednesday's elections.
Mugabe reportedly secured his grip over the country today after his party ZANU PF won a two-thirds majority in parliament.
Robert Mugabe has secured his grip on power in Zimbabwe today after his party ZANU PF won a majority in parliament in Wednesday's election.Read the full story ›
Robert Mugabe's Zanu-PF has won the election by a two-thirds majority in parliament, according to the Agence France Presse agency.
Zimbabwe's Movement for Democratic Change (MDC) has said it could take to the streets to challenge President Mugabe's victory in elections it rejects as a farce.
"Demonstrations and mass action are options," party spokesman Douglas Mwonzora said.
Regional inter-governmenal organisation SADC (Southern African Development Community) have called on Morgan Tsvangirai to accept results of Zimbabwe's election, and said the poll should not be nullified, the Tanzanian foreign minister told Reuters.
The Southern African Development Community says the Zimbabwean elections were "free and peaceful," but it will not make judgement on fairness right now.
Observers from regional inter-governmental organisation SADC (Southern African Development Community) are very positive about the Zimbabwean elections, despite the widespread concern of many others.
The African Union has said it is reserving judgement on whether Zimbabwe's elections were systemically flawed until further details of the disputed vote are clarified.
The head of the AU's observer mission, Olusegun Obasanjo said that voting was peaceful, and that "could have been avoided and even tended to have breached the law."
The mission is asking authorities to investigate reports that large numbers of eligible voters were turned away from polling stations on Wednesday.
The head of the African Union observer mission in Zimbabwe has said the elections were "free, honest and credible," the BBC reports.
Olunsegun Obasanjo said the incidents reported during Wednesday's poll, including allegations of widespread fraud and thousands of voters being turned away during polling, could not "change the outcome."