Port-au-Prince, Haiti ? Scuffles broke out and polling stations opened hours late Tuesday as masses of Haitians waited – sometimes in mile-long lines – to vote under the protection of U.N. peacekeepers crouching behind machine guns and patrolling alongside armored vehicles.

Outside the gang-controlled Cite Soleil slum, frustrated voters pounded on empty ballot boxes and chanted, “It’s time for Cite Soleil to vote!”

Rene Preval, a 63-year-old former president backed by many poor Haitians, is the front-runner, according to pre-election polls. In an interview with The Associated Press, he said: “People are investing everything in this election.”

Also among the 33 presidential candidates are a factory owner whose slogan is “Order, Discipline, Work,” and another former president ousted in a coup.

Turnout for the vote – called a key step toward steering this bloodied, impoverished nation away from collapse – all but overwhelmed electoral officials. At dawn, when the 800 polling stations were supposed to open, it immediately became apparent the day would not go smoothly. In the upscale Petionville suburb of the capital, members of a crowd of thousands of voters stormed a voting station. Several women fainted.

Brazilian U.N. peacekeepers close the gate of the polling station where residents of the Cite-Soleil slum were voting in Port-au-Prince, Haiti. Masses of Haitians flocked to polls Tuesday to vote in an election aimed at restoring democracy in the impoverished nation.

Polls closed by late Tuesday – nearly four hours later than scheduled.

Election authorities said the problems were largely limited to Port-au-Prince. By early afternoon, all polls across this country of 8.3 million were open, said U.N. spokesman David Wimhurst.

Most voters waited in lines for hours in the capital of the Western Hemisphere’s poorest nation, but some angrily roamed the streets, fuming at being turned away because of myriad problems.

“If these elections are not fair and if the person whom the population wants doesn’t win, houses will burn and heads will be cut off,” said Jean Pierre, an unemployed 33-year-old man.

The stakes are huge – more than simply who will lead the country and who will occupy seats in parliament. Haiti, which has seen only one president complete his term in office, could implode if the elections go wrong, experts say.