The U.S. National Hurricane Center in Miami said Earl strengthened into a Category 2 storm with maximum sustained winds of 160 km/h, and was expected to continue picking up steam as it moved near the northern Leeward Islands.

Steady bands of rain began lashing islands including Antigua, where the Grand Pineapple Beach Resort on the north side battened down early for the night and tourists sought shelter inside their rooms.

Winds were heavy Sunday but had not caused any major damage, and the surf was higher than normal but not punishing, general manager Courtney Miller told The Associated Press by phone.

Center forecasters said Earl could strengthen into a major hurricane as soon as Monday — probably while east of Puerto Rico. Major hurricanes are those Category 3 and higher.

Islanders set up emergency shelters and airlines cancelled flights as Earl churned toward the northern Caribbean on Sunday. Cruise lines diverted ships to avoid the storm's path.

People on several islands stuffed shopping carts with bottled water, canned food, milk, candles and batteries, while some tourists scrambled to board flights home. Others enjoyed the beach while they could.

"I'm just trying get a good suntan in while the weather is still co-operating," said Linda Curren of New York City, sunbathing on San Juan's Ocean Park beach as a few surfers paddled into pounding waves.

In Antigua, the V.C. Bird International Airport closed, while regional airlines LIAT and Winair suspended flights. Cruise ships diverted to other ports in the Caribbean and Mexico.

In St. Kitts and Nevis, authorities urged islanders to take all necessary precautions for the approaching hurricane, which is dwarfing the tiny island nations and territories of the northern Caribbean.

Meanwhile, Hurricane Danielle was bringing dangerous rip currents to the U.S. East Coast.

Forecasters warn that as a hurricane, Earl could bring battering waves and storm surge reaching up to one metre above normal tide levels in some areas.