HAVANA, Cuba (AP) — Tropical Storm Isaac pushed over Cuba yesterday after sweeping across Haiti's southern peninsula, where it caused flooding and at least four deaths, adding to the misery of a poor nation still trying to recover from the terrible 2010 earthquake.

Isaac's centre made landfall just before midday near the far-eastern tip of Cuba, downing trees and power lines. In the picturesque city of Baracoa, the storm surge flooded the seaside Malecon and a block inland, destroying two homes.

Forecasters said Isaac poses a threat to Florida Monday and Tuesday, just as the Republican Party gathers for its national convention in Tampa. It could eventually hit the Florida Panhandle as a Category 2 hurricane with winds of nearly 100 mph (160 kph).

Florida Governor Rick Scott declared a state of emergency, officials urged vacationers to leave the Florida Keys, and the US National Hurricane Centre said a hurricane warning was in effect there, as well as for the west coast of Florida from Bonita Beach south to Ocean Reef and for Florida Bay.

At least four people were reported dead in Haiti, including a 10-year-old girl who had a wall fall on her, according to the country's Civil Protection Office. There were no immediate details on how the others died.

The Government also reported two injuries; "considerable damage" to agriculture and homes; nearly 8,000 people were evacuated from their houses or quake shelters; and that more than 4,000 were taken to temporary shelters.

Many, however, stayed and suffered.

The Grive River overflowed north of Port-au-Prince, sending chocolate-brown water spilling through the sprawling shantytown of Cite Soleil, where many people grabbed what possessions they could and carried them on their heads, wading through waist-deep water.

"From last night, we're in misery," said Cite Soleil resident Jean-Gymar Joseph. "All our children are sleeping in the mud, in the rain."

Scores of tents in quake settlements collapsed, including more than 50 in Cite Soleil, forcing people to scramble through the mud to try to save their belongings.

About 300 homes in Cite Soleil lost their roofs or were flooded three feet (one metre) deep, according to Rachel Brumbaugh, operations manager for the US non-profit group World Vision.

Doctors Without Borders said it anticipated a spike in cholera cases due to the effects of flooding and it was preparing to receive more patients.

The international airport reopened by the afternoon, but there was still extensive flooding throughout Port-au-Prince after 24 hours of steady rain.

Forecasters predicted the storm would likely march up through the Gulf of Mexico and approach the Florida Keys today, then continue north off the state's west coast as a hurricane tomorrow, just as the Republican National Convention is scheduled to start.

Tampa is within the tropical storm watch zone, meaning forecasters believe tropical storm conditions are possible there within the next 48 hours.

Governor Scott said during a media briefing that delegates were being told how to stay safe during a storm, and officials were ready for storm surge, bridge closures and other problems that could arise during the convention.

After hitting land near the easternmost tip of Cuba yesterday, Isaac's centre spent just a few hours over the island before re-emerging into the water, where it was expected to pick up strength.

Yesterday afternoon, the storm was centred about 120 miles (195 kilometres) east of Camaguey, Cuba, with maximum sustained winds of 60 mph (95 kph), the Hurricane Centre reported. It was moving northwest along the Cuban coastline at 21 mph (33 kph).

Tropical storm-force winds extended nearly 205 miles (335 kilometres) from the centre, giving Isaac a broad sweep as it passed.