Protesters attacked a cholera treatment centre as it was preparing to open in the city of St. Marc on Tuesday, highlighting the fear surrounding a disease that was almost unknown in Haiti before it began spreading through the countryside, aid workers said.

Some of the roughly 300 students and other protesters said they feared the Doctors Without Borders-Spain clinic would bring more of the disease to their seaside town, which is one of the hardest hit in the week-old epidemic that has killed 284 people and infected 3,769, according to United Nations figures.

Witnesses said the protesters threw rocks and at least one Molotov cocktail. UN peacekeepers from Argentina arrived with riot shields to reinforce police.

Warning shots were heard and the UN said its soldiers fired blanks. There were no reports of injuries.

Haitian health officials assured the crowd the clinic would not open in that neighbourhood.

The 400-bed facility was intended to rehydrate and treat people with the severe diarrheal disease.

Doctors Without Borders-Spain country chief Francisco Otero said the group had consulted with local authorities and told them the clinic is important for stemming the spread of cholera. He said they would try to reopen it in another part of St. Marc.

"In the coming days we are going to start to work with this community, to explain that there is no risk for them to have such a facility," Otero told The Associated Press.

25 more deaths

More than 420 new cholera cases were confirmed Tuesday, according to the UN Office for the Co-ordination of Humanitarian Affairs. Twenty-five more deaths were confirmed, bringing the total to 284.

OCHA spokeswoman Imogen Wall says most of the cases occurred along the central Artibonite River with many new instances in Haiti's central plateau. St. Marc's main hospital was the first to widely alert the epidemic as it overflowed with the sick and dying.

Haitian television aired footage of emaciated patients and parents grieving for children lost in the epidemic over mournful music on Tuesday afternoon. The programs were reminiscent of montages from earlier this year about the earthquake.

UN staff have been told to avoid areas of heavy infection unless they are given special permission to go there. Guatemalan police manned a checkpoint Tuesday on the highway from Port-au-Prince to Mirebalais, a hard-hit city in central Haiti, to make sure unauthorized UN vehicles did not pass.

Trying to contain disease

Aid workers, meanwhile, scrambled to contain the spread of the disease, which had not hit Haiti for generations.

Speaker trucks passed through neighbourhoods in the capital, where a handful of cases have been confirmed in people who apparently contracted it in the countryside, advising the city's millions of residents to wash their hands.

The Dominican Republic, which borders the central plateau where many new cases are being found, announced that all people crossing the border must wash hands and complete a medical form. They also stepped up military surveillance and closed a twice-weekly binational market Monday, sparking protests on the Haitian side of the border.