Heavy rains, mudslides and flooding in Haiti have killed at least 23 people, just days into the six-month-long Atlantic hurricane season.

Haiti's civil protection agency said Tuesday most of the deaths occurred in the capital, Port-au-Prince, where a week's worth of torrential downpours has turned streets into rivers and forced people to flee to their rooftops.

But the rains have also inundated the crowded slums and tent camps where thousands of people remain after losing their homes during Haiti's devastating earthquake last year.

Aid agencies are warning the flooding could aggravate the cholera outbreak that has killed thousands since October.

Haiti's new president, Michel Martelly, is urging residents to keep calm as the storm passes over the battered nation, the Western Hemisphere's poorest.

The storm is sweeping across other countries in the Caribbean, and forecasters are warning of possible flash floods in the Dominican Republic, which shares the island of Hispaniola with Haiti, as well as Cuba and Jamaica. In the Dominican Republic, more than 8,000 people have been evacuated.