Election officials shut down polling places in one of Haiti's 10 administrative regions after protesters raided voting sites and dumped ballots in the streets.
The incident was reported Sunday in the central plateau town of Mirebalais in the Central District. There also was a report of a gunman who tried to intimidate voters.
Haitians voted Sunday in senatorial elections that were delayed by political turmoil and a series of hurricanes last year. The election will fill 12 seats in Haiti's 30-member senate.
Observers said turnout was very light. Supporters of former President Jean Bertrand Aristide urged Haitians to stay home in protest. The provisional electoral council disqualified all candidates from Mr. Aristide's Fanmi Lavalas Party, which is widely backed by the country's poor.
The council disqualified the Lavalas candidates earlier this year because their papers did not have Mr. Aristide's signature.
Although Mr. Aristide was deposed in a 2004 coup and now lives in exile in South Africa, some Haitians are calling for his return.
Mr. Aristide's former protégé, René Preval, is now president of Haiti, the poorest country in the Western Hemisphere.
Some information for this report was provided by AP and Reuters.