Musician Michel Martelly has accused President René Préval’s party of fraud after ruling party candidate Jude Célestin made it through to the second round, leaving Martelly in third place.
In continuing violence, the offices of Célestin’s Inite party were set on fire in the capital Port-au-Prince, and UN peacekeepers used tear gas and fired bullets in the air to disperse a crowd in the Pétionville area of the capital.
Canada has closed its embassy and the United States is warning citizens against all
non-essential travel to Haiti. International flights to and from Port-au-Prince have been suspended.
Célestin has called on his supporters to not to use violence but to protest.
"We believe that the election cannot be contested through destruction,” he said. “We demand that you remain calm but mobilise across the country, because we will legally defend your votes.”
Tuesday's initial results showed former first lady Mirlande Manigat in the lead with 31.37 per cent (336,378 votes), Célestin second with 22.48 per cent (241,462 votes), and Martelly third with 21.84 percent (234,617 votes).
The ruling party also won a landslide victory in the parliamentary polls on 28 November.
The second round presidential election is scheduled for 16 January.
Meanwhile, a cholera epidemic that has killed more than 2,100 people in the last six weeks is still spreading. A US-Haitian study published Thursday in the New England Journal of Medicine said the outbreak was likely caused by a bacterial strain from South
Asia and resembled a type of cholera found in Bangladesh in recent years.
The authors of the study said they had not yet determined the precise source. The Nepalese army and the UN mission have said there is no evidence that peacekeepers are to blame, as a French expert has claimed.