At least one person was killed and several were wounded when gunmen opened fire on an election rally in Haiti for presidential candidate Michel Martelly.
The United Nations police force confirmed the incident happened in southern Haiti but has been unable to give a number of victims.
Mr Martelly, a popular singer widely known as "Sweet Micky", is one of the leading candidates in Sunday's election, in which nearly 4.7 million Haitians are eligible to vote.
Haiti's next president faces the daunting task of rebuilding a nation of 10 million that was already the poorest in the Americas before an earthquake in January flattened much of Port-au-Prince and claimed 250,000 lives.
A cholera epidemic has since claimed more than 1600 lives.