Some cried fraud, and thousands of U.N. peacekeepers stood watch, as balloting began hours late at some stations, infuriating poor supporters of ex-president Rene Preval, a one-time Aristide ally who is favored to win.

"Give me my polling center to vote Preval," said Jean Nazaire outside a closed voting center in the capital's Delmas area. "They told us to wake up early to go to vote. Many of us didn't sleep at all. Why can't they give us our chance?"

A 75-year-old man died in a crush at one center near the upscale Petionville suburb. About 20 people suffered minor injuries when voters charged through the gates of another in downtown Port-au-Prince.

Official results may not be known for days and the chaotic start marred an election that could prove troublesome for U.S. policy in the impoverished nation of 8.5 million people.

Critics accused Aristide of despotism and Washington pressed him to leave during a bloody rebellion in 2004 only to find his one-time ally now favored to retake the presidency.

There was disappointment and anger for thousands who rose before dawn and marched past rooting pigs, smoking garbage and U.N. armored personnel carriers to get to a voting station near the teeming Cite Soleil shantytown.

When the center failed to open at 6 a.m. (1100 GMT), they charged up and down the streets, waving tree branches and chanting Preval slogans.

The center finally opened, nearly 3 1/2 hours late.

FRAUD FEARS

Some voters suspected fraud, charging that voters in wealthier neighborhoods were already casting ballots for Preval's top rival, businessman Charles Baker, while slum dwellers waited.

"In Petionville, the bourgeois is voting but we are not allowed. We know their fraud. They are trying to give us Baker," said Lucas Charles. "If they give us Baker, we will spend the next five years firing weapons."

Haitian police used tear gas to control an unruly mob outside a polling station in Delmas, witnesses said.

Exactly 20 years after the dictatorial rule of Jean-Claude "Baby Doc" Duvalier crumbled, Tuesday's vote offered what the United Nations views as hope for an end to the coups and instability that have crippled Haiti since then.

A new round of fighting, however, could plunge the poorest country in the Americas into even deeper chaos.

Many Haitians suspect the unelected interim government has tried to make voting as difficult as possible in poor areas to hurt Preval. Callers inundated local radio stations, trying to find their polling stations. Many said they were not told where to cast ballots and others had to walk several miles.

Gerard Latortue, the interim prime minister, admitted there were problems but said the government was "happy that despite those problems people have turned out massively to vote."

Preval draws support from the miserable slums where Aristide was strongest. He was president from 1996 to 2001, an era of relative calm between Aristide's two terms, and he is Haiti's only elected leader to complete his term and hand over power peacefully.

But he is opposed by the same wealthy elite that helped drive Aristide from power.

Preval held a comfortable lead in opinion polls but needs to win more than 50 percent of the votes to avoid a run-off next month. Polls close at 4 p.m. (2100 GMT).

Preval's main rivals are Baker, an industrialist, and Leslie Manigat, who was president for a few months in 1988 before being deposed in a military coup. There are 33 presidential candidates, but most stand no chance.

The voting took place under the watchful eyes of a 9,000-strong U.N. peacekeeping force sent to Haiti after Aristide left.

Violence that has killed hundreds since Aristide was deposed and a wave of kidnappings in the capital forced authorities to postpone the election several times.

But pro-Aristide gang leaders blamed for much of the insecurity recently changed tack by backing the poll. With that, the level of violence and crime dropped dramatically.

Still, experts say Haiti is awash with weapons and Preval's supporters could turn violent if he loses or they suspect fraud. On the other side, anti-Aristide armed groups could try to disrupt the election to keep Preval out of power.