The UN mission in Haiti has issued a statement expressing its, and some foreign countries', deep concern at the numerous incidents that marred the elections.
In the grip of a cholera epidemic that has claimed 1,650 lives, and the death of 250,000 people in an earthquake in January, Haitians are choosing a successor to President René Préval.
Despite street protests and calls for the vote's cancellation, the Provisional Election Council (CEP) late Sunday validated the election in all but 56 of the country's 1,500 polling stations.
Fears that fraud could mar the elections were realised even before polls closed with 12 out of 18 of the presidential contenders denouncing a "conspiracy" between Preval's government and the electoral commission.
The dissenters include the poll favourite and former first lady Mirlande Manigat, who accused the alleged conspirators of seeking “to steer the elections to benefit the candidate of the party in power".
Several thousand demonstrators took to the streets of the capital Port-au-Prince to protest the alleged vote-rigging.
In the US, the Centre for Economic and Policy Research said Haiti’s vote was fraught with widespread irregularities and should be rejected by the international community.