Tegucigalpa - More than 5 000 supporters of leftist Honduran presidential candidate Xiomara Castro protested on Sunday demanding a recount of the ballots cast last week, in a vote her campaign alleges was "stolen".
Castro, wife of former president Manuel Zelaya lost by eight percentage points, according to official election results.
Conservative candidate Juan Orlando Hernandez was the winner with 36.8% of the vote.
But on Friday, Castro claimed that victory was "stolen" from her, and that she had "proof of the disgusting monstrosity".
Protesters marched downtown in the capital and gathered outside the office of the electoral tribunal, where election materials are stored.
Supporters carrying the coffin of a slain party activist led the march, amid chants of "murderers", "the blood of martyrs is the seed of freedom" and "fraud". They waved the Libre Party's red and black flag.
Zelaya, who was ousted in June 2009 coup, stood on the vehicle carrying the coffin and said Castro's campaign would file papers on Monday for "a review of all the records and all the polls".
And if the tribunal refuses and "they don't resolve the dispute, we will appeal to all the levels permitted by law, and if they don't resolve it, we will also appeal to international treaties," he said.
Castro said that, since 2009, more than 200 members of the leftist group that opposed the coup have been killed.
"We are ready to continue the fight in peace," she said.
"We will continue knocking on the doors of the tribunal," added Castro, who called herself the president of Honduras.
Around 100 riot police wielding shields, batons and tear gas guarded the electoral tribunal office, but the demonstration ended without incident.
The slain activist, aged 58-years-old Jose Antonio Ardon, was shot dead late on Saturday, according to Libre Party officials, who said he was attacked by four gunmen about a block from his home.
Ardon, who was a member of the party's "Motorizada," a group that spread party messages on motorcycles, was buried later on Sunday at a ceremony attended by some 300 people waving Libre party flags.
European Union and Organisation of American States observers had called the elections transparent. So did the US-based Carter Centre.
But renowned Spanish judge Baltasar Garzon, who witnessed the voting, said there was in fact electoral fraud using various means and methods.
And an Austrian official with the EU observers said that while their preliminary report may have concluded the elections were transparent, many disagreed.
As president-elect, Hernandez inherits a country of 8.5 million people with 71% of the population living in poverty and a soaring homicide rate of 20 murders per day, one of the deadliest in the world.