(Adds protests overnight, comments from protester, comments from rival Salvador Nasralla)
TEGUCIGALPA, Nov 30 (Reuters) - Honduran protesters set up barricades and clashed with police near a vote-counting center on Thursday, following a widely criticized presidential election that produced no clear result in four days and which the opposition says was fraudulent.
Both President Juan Orlando Hernandez and his rival Salvador Nasralla, a television game show host allied with leftists, claimed victory after Sunday's election, which first favored the opposition candidate but then swung and put the incumbent ahead after a hold-up in the count.
International concern has mounted over a growing political crisis in the Central American nation, whose other challenges include poverty, drug gangs and one of the world's highest murder rates. Only eight years ago, Honduras saw a military-backed coup.
The Organization of American States (OAS) appeared to have salvaged the credibility of the election on Wednesday by eliciting signed statements from both candidates vowing to respect the final result once disputed votes had been checked.
A few hours later, however, Nasralla, who initially held a five-point lead, rejected the OAS accord he had signed, saying his opponents were trying to rob him. He urged supporters to take to the streets of the capital Tegucigalpa to defend his triumph.
"They take us for idiots and want to steal our victory," said Nasralla, who heads a left-right coalition.
His followers heeded his call, with protests throughout the night across the country. In the city of La Ceiba, protesters set up barricades and burned tires across a bridge and blocked at least two other motorways.
In capital city Tegucigalpa, police fired tear gas to disperse Nasralla supporters who were peacefully gathered outside the election tribunal where the vote was being counted.
The fumes entered the building, prompting the evacuation of staff. Clashes between police and masked protesters continued through the night.
"We're going to keep protesting and won't let them steal this victory," 20-year-old university student Josue Valladares said on Thursday, as votes were being counted on the other side of a human wall of riot police.
"Hernandez should respect the popular will and hand over power," Valladares said.
Nasralla took to Twitter early Thursday to implore his followers to protest peacefully and not be "provoked by Hernandez's activists."
The sporadic way in which results have been published, and the reversal of Nasralla's lead have led to allegations that Hernandez may have influenced the tribunal.
The president has consolidated power in recent years and is the first president to seek a second term since a 1982 return to democracy.
Hernandez says the change in vote tendency reflects his support in rural areas, from where ballots were slower to arrive in the city.
On Monday, the tribunal published more than half the results, showing Nasralla with a five point lead, but then published nothing more for 36 hours.
When the count finally started again, Hernandez began to reel in Nasralla. The count has started and stopped ever since, with the tribunal blaming a delay Wednesday on computer glitches.
On Thursday, with 88.75 percent of ballots counted, the center-right Hernandez had secured 42.48 percent of the vote, while Nasralla had 41.71 percent, the tribunal said.
International observers said the delays were damaging the credibility of authorities, and risked undermining the winner's legitimacy. The U.S. State Department said the tribunal should be allowed to work without interference.
Ahead of the election, opinion polls indicated that Hernandez was favored to win the vote in the poor Central American country of more than 9 million people
Nasralla is one of Honduras' best-known faces and is backed by former President Manuel Zelaya, a leftist ousted in a coup in 2009 after he proposed a referendum on his re-election. (Editing by Simon Cameron-Moore and Bernadette Baum)