Supporters of the candidate leading in the election to become Haiti's president are getting increasingly angry at the slow counting of the ballots.

The first presidential election since Jean-Bertrand Aristide was forced to leave the country after a rebellion in 2003 was held on Feb. 7, but five days later, the votes are still being counted.

Supporters believe that René Préval won the vote, but with only 75 per cent of the ballots counted, they worry that the electoral council is trying to block his victory.

Supporters of René Préval wave a flag with his photo in Port-au-Prince on Saturday. (AP Photo/Ariana Cubillos)

Council officials have denied that, although one told the Associated Press on Sunday that he feared the count had been manipulated. He did not accuse anyone of wrongdoing.

Pierre Richard Duchemin, an electoral council member, called for an investigation. He told AP that "there is an effort to stop people from asking questions" about how the votes were counted.

Préval has more than 49 per cent of the votes counted so far, but that leaves him just short of the key number, 50 per cent plus one.

Unless he passes that, he will face a runoff election in March against second-place candidate Leslie Manigat, who has less than 12 per cent. No other candidate is even close.

Préval backers are worried that the huge number of invalid ballots – about 125,000, or 7.5 per cent of the total – show the electoral council is biased against their candidate.

Council officials have said that the invalid ballots were blank or not clearly marked.

On Sunday, thousands of Préval supporters danced and sang in the streets of the capital, Port-au-Prince.

They chanted: "We've already voted. We aren't voting again!"

They gathered in front of the electoral council's office, where the Haitian national security police stood guard.

They called on the council to get the votes counted.

• FROM FEB. 7, 2006: Massive turnout overwhelms Haitian election officials

The demonstrations were peaceful but marchers warned that they are becoming very frustrated, and violence could break out.

Some demonstrators said if Préval isn't declared president on the first ballot, they won't vote again because they believe the whole process is a fraud.

Préval, who was president from 1996 to 2001, is the favourite of many of Haiti's poorest people.

His backers hope he can stablize the country and end the violence that pervades the Caribbean nation. Despite the presence of UN forces, armed gangs roam the streets and violent incidents are common.