Ballot boxes were ripped up and voting papers strewn in the streets, polling stations opened late and were ransacked, and voters could not find their names on lists.
The 12 politicians gathered in a hotel ballroom in the capital Port-au-Prince to join hands, denounce Jude Celestin, the chosen candidate of president René Préval, and call for the election to be cancelled.
They accused Mr Préval of conspiring to “perpetuate his power and keep the people hostage to continue their misery”. A crowd outside, which burst into Haiti’s national anthem when the candidates arrived, chanted: “Arrest Préval!”
Crowds surged through the streets carrying tree branches and campaign posters, calling the election a sham and claiming victory for their various candidates.
The international community had hoped the election would produce a legitimate government in the country devastated by an earthquake in January and a cholera epidemic that has killed more than 1,600 people. The UN said there had been “numerous incidents that marred the elections”.
Haiti’s electoral council said the candidates’ protest had no legal weight, adding that there had been problems at only 56 of nearly 1,500 voting centres. A final result is not expected until December 7 and run-offs are expected for nearly all the seats.