Hurricane Irene buffeted Puerto Rico with winds and torrential rain on Monday, knocking out power and downing trees as it churned westward on a track that will threaten Florida by the end of the week.

Local media in the US Caribbean territory reported that about 600 people took refuge in shelters, and electricity was knocked out across half of the island, including the capital, San Juan, affecting some 800,000 people.

Trees were blown down, rivers overflowed and coastal roads were flooded. But there were no immediate reports of deaths or serious casualties.

Governor Luis Fortuno said the worst-hit area was the east coast, from Fajardo to Yabucoa, and he had asked the US government to declare Puerto Rico a disaster area so it can gain access to emergency funds.

'This turned into a hurricane in a matter of 24 hours and crossed the entire island,' Fortuno said. 'This shows we need to be prepared when these systems approach.'

At 1300 GMT, Irene, carrying winds of 130 km per hour, was moving away from Puerto Rico and would approach northern coast of Dominican Republic later in the day, the US National Hurricane Center said. It was heading for the southeastern Bahamas.

On Monday morning, rains and winds had already eased in San Juan and the airport was expected to reopen.

Irene, the first hurricane of what has been a busy but non-destructive 2011 Atlantic season to date, formed earlier on Monday over Puerto Rico.

The NHC's general forecast shows the hurricane nearing South Florida by late on Thursday and early on Friday after passing over the Turks and Caicos Islands and the Bahamas.

Most computer forecast models show Irene swinging up parallel to Florida's east coast with possible eventual landfall on the Georgia or South Carolina coast early on Saturday.

A few models show the hurricane shifting farther west up the Gulf of Mexico coast of the Florida peninsula.

NHC wind speed predictions indicated Irene, currently a Category 1 hurricane on the five-step Saffir-Simpson intensity scale, could come close to being a major Category 3 hurricane by the weekend.

Puerto Rico had lifted a ban on Sunday morning shopping, allowing stores to open so residents could stock up on canned food, bottled water and other necessities. Prices were frozen and alcohol sales were halted until after the storm passes.

Schools and government offices were closed for Monday in the US territory of 3.9 million people.

Fortuno rushed back to Puerto Rico on Sunday from North Carolina, where he was named chairman of the Southern Governors Association.

In the Dominican Republic, authorities warned of abnormal waves up to 4.5 metres high.

Weeks of heavy rainfall have already caused deadly flooding in the Dominican Republic and authorities had said they may issue evacuation orders for vulnerable areas on Monday.

Residents of the Southeastern United States were urged to monitor Irene's progress as the storm headed their way.-Reuters