Haiti's electoral authority has postponed Sunday's planned presidential run-off amid mounting opposition street protests and voting fraud allegations.
Pierre-Louis Opont, chairman of the Provisional Electoral Council (CEP), said Friday that the vote had been pushed back because of "obvious security concerns."
Opont complained that CEP personnel had been attacked and that several polling stations had been burned overnight.
The poorest country in the Americas had been due to go to the polls to elect a successor to President Michel Martelly and seek a way out of a deep political crisis.
But opposition activists fear the poll will be rigged in favor of Martelly's hand-picked successor, Jovenel Moise, and their champion Jude Celestin is boycotting the vote.
Angry crowds have gathered in the capital Port-au-Prince, burning cars, clashing with police and threatening to disrupt any attempt to allow voting to go ahead.
The decision will be seen as a blow to the ambitions of the United States, Haiti's key foreign partner, which had pushed for voting to go ahead despite the violence.
Martelly, who has denounced the protests and accused critics of trying to destabilize Haiti, was due to broadcast an address to the nation later in the day.
The former popular singer is barred from seeking re-election and has vowed to hand over power to a successor on February 7 in accordance with the constitution.
In October's first round vote, Martelly's hand-picked ally Moise was credited with 32.76 percent of the vote over opposition flag-bearer Celestin's 25.29 percent.
But many polling stations remained closed due to unrest or electoral skullduggery and voter turnout was tiny.
Celestin's supporters cried foul, accusing Martelly of mounting an "electoral coup d'etat."
The government allowed a hastily assembled independent commission to review the ballots, but the opposition has not been mollified and protests have erupted.
"On the 24th, it's 'No'," Celestin told AFP this week. "I won't take part in this farce, it will be a selection not an election because there will only be one candidate."
Political impasse
On Monday, Tuesday and again on Friday protesters descended onto the streets of Port-au-Prince, a capital still scarred by a 2010 earthquake that left more than 200,000 dead.
They blocked several downtown streets and fought running battles with police.
This week, an umbrella body of poll observers declared they would not take part in an event "that the CEP wants to pass off as an election."
On Tuesday, observers from the Organization of American States, expressed "concern on the current political impasse ahead of Sunday's second round of elections."
The US State Department had no immediate reaction to news that Sunday's poll had been canceled.
But on Thursday, spokesman Mark Toner had said Washington wanted voting to go ahead while also supporting "efforts to dialogue among Haitian actors to enhance the credibility and transparency of the electoral process."
But for his part, Martelly did not appear in the mood for dialogue and negotiation, denouncing instead a "vast plot to try to destabilize us."
He accused the opposition of trying to run out the clock to undermine the legitimacy of the planned handover of power.
"They want to take power their way, because they can't take it through the ballot," he alleged earlier in the day in a radio address.
Haiti has seen its share of chaos.
Since 1986, when president-for-life Jean-Claude "Baby Doc" Duvalier fled a revolt, the Caribbean island nation has struggled repeatedly to hold credible elections.
To political chaos and gang violence has been added the fury of nature, with first the earthquake and then a cholera epidemic ravaging the population.
