Riot police fired shots in the air to try to disperse the demonstrators, who shouted that Rene Preval must go.
A deciding second round of Haiti's presidential election is scheduled to be held on 20 March to choose a successor to Mr Preval, whose mandate formally ends on Tuesday.
Mr Preval has parliamentary approval to stay on if necessary until mid May so he can hand over to an elected successor.
However opponents want him to step down in favour of a provisional government.
