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.
Members of Zimbabwe's opposition say they have been targeted by Mugabe supporters following the president's re-election.
President Robert Mugabe's declaration as winner has been met by international concern over the conduct of the African nation's poll.
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.