PORT-AU-PRINCE (Reuters) – Thousands of protesters rampaged through Haiti’s capital and other cities on Wednesday, hurling stones and wrecking property in a wave of unrest against election results they say were rigged by the ruling government coalition.

At least two people were killed in the flaring violence, which appeared to dash international hopes that the U.N.-backed elections held on November 28 could create a stable new leadership for Haiti, an impoverished nation struggling to recover from a devastating January earthquake.

Port-au-Prince descended into chaos as supporters of popular musician and presidential candidate Michel Martelly, who failed to qualify for an election run-off in results announced by electoral authorities, set up burning barricades of timber, boulders and flaming tires across the city.

Protests in which some government buildings were torched were also reported in other cities in the volatile Caribbean country.

A local mayor in the south coast city of Les Cayes, Jean Mario Altenor, said two people were killed by U.N. peacekeepers when protesters tried to burn a local elections bureau. A U.N. police spokesman said he had heard of two reported deaths but had no information about how these had occurred.

Haitian media also reported another person killed in protests in Cap-Haitien in the north.

Haiti’s outgoing President Rene Preval, U.N. Secretary-General Ban Ki-moon and Canadian Foreign Minister Lawrence Cannon all appealed for calm, urging election candidates with grievances to address them through the legal channels provided by the country’s electoral laws.

“Breaking everything, destroying everything is not going to solve the problem,” Preval said in Port-au-Prince.

Police fired tear gas to prevent a stone-throwing mob from reaching the offices of the Provisional Electoral Council (CEP) in the Petionville district of the capital, witnesses said.

Preliminary results from the turbulent November 28 elections announced late on Tuesday showed former first lady Mirlande Manigat and Preval’s protege, Jude Celestin, going through to the January run-off, with Martelly narrowly in third place and so excluded.

But these results flew in the face of voting returns previously cited by media and Haitian election observers that had shown Manigat and Martelly as the two run-off qualifiers, not government technocrat Celestin. Martelly had already accused Preval and Celestin of trying to rig the results.

The United States, through its embassy in Port-au-Prince, cast doubt on the CEP results late on Tuesday, saying it was concerned they were “inconsistent with” vote counts observed by “numerous domestic and international observers.”

Rebuffing the U.S. statement, Preval said the electoral council was the sole arbiter of election disputes. “Just because people are protesting in the streets, the council can’t just change one set of results for another,” he said.

“ALLEGATIONS OF FRAUD”

U.N. chief Ban expressed concern about what he called “allegations of fraud.” “He also notes that these results are not final and are subject to the provisions stipulated in the electoral law,” U.N. spokesman Martin Nesirky said.

Under Haitian electoral law, candidates have 72 hours in which to formally challenge the announced results.

The protesters in Port-au-Prince set fire to the headquarters of Preval’s ruling (Inite) coalition. Businesses and schools stayed closed and many fearful residents stayed home, off the rubble-strewn streets. There was no traffic apart from an occasional police or U.N. vehicle.

Local police appeared to be overwhelmed by the numbers of protesters. U.N. peacekeepers of the more than 12,000-strong U.N. force in Haiti were not seen intervening in the capital.

At least one U.N. helicopter clattered overhead.

Plumes of black smoke rose above the sprawling, crowded city, which bears the scars of the January 12 earthquake that killed more than 250,000 people in the Western Hemisphere’s poorest state. Haiti is also battling a cholera epidemic.

Ban expressed concern about the violence. “A peaceful solution to the current situation is crucial not only to confront the cholera epidemic in the short term but also to create the conditions in the medium term for recovery and development from the earthquake,” his statement said.

The protests erupted in the Petionville, Delmas and Canape Vert districts of the capital, among other areas.

Local radio reported protests in the southern town of Les Cayes in which Martelly supporters burned down government buildings, including the tax and customs offices.

Enraged Martelly supporters tore down, or hurled stones at election posters of Celestin and also of Manigat.

“It’s not money that gives power, it’s the people that should give power,” said one protester, Lafranche Schneider.

“Hang Preval!” other protesters yelled.

“CRITICAL TEST”

American Airlines suspended flights to and from Haiti. Port-au-Prince’s airport appeared to be closed.

“The 2010 elections represent a critical test of whether the Haitian people will determine their destiny through their vote,” the U.S. embassy said in its statement.

The U.N. mission in Haiti (MINUSTAH) and a joint Organization of American States/Caribbean Community election observer mission had given a cautious initial endorsement of the vote, despite acknowledging irregularities.

The Provisional Electoral Council said Manigat won 31.37 percent of the first-round votes ahead of Celestin with 22.48 percent. It put Martelly less than one percentage point behind Celestin at 21.84 percent.

This was on the basis of just over a million votes counted, out of a total of 4.7 million registered potential voters.

The second round has been provisionally set for January 16, but the date has to be confirmed by electoral authorities.

(Additional reporting by Allyn Gaestel in Port-au-Prince and Patrick Worsnip in New York; Writing by Pascal Fletcher; Editing by Eric Beech)