SANTO DOMINGO, Dominican Republic — French, British and Dutch rescuers rushed aid to a heavily damaged string of Caribbean islands Thursday after Hurricane Irma left at least seven people dead and thousands homeless as it spun toward Florida for what could be a catastrophic blow this weekend.

Warships and military planes were dispatched with food, water and troops after the fearsome Category 5 storm smashed homes, schools and roads, laying waste to some of the world’s most beautiful and exclusive tourist destinations.

Hundreds of miles to the west, Florida braced for the onslaught, with forecasters warning Irma could slam headlong into the Miami metropolitan area of 6 million people, punish the entire length of the state’s Atlantic coast and move into Georgia and South Carolina.

More than a half-million people in Miami-Dade County were ordered to leave as Irma closed in with winds of 175 mph (281 kph).

“Take it seriously,” said Maj. Jeremy DeHart, a U.S. Air Force Reserve weather officer who flew through the eye of Irma at 10,000 feet. “Because this is the real deal.”

By Thursday afternoon, the hurricane was north of the Dominican Republic, where authorities reported some flooding and the evacuation of several thousand locals and tourists but no serious damage or casualties.

Skies over the Haitian capital, Port-au-Prince, were still clear just after noon local time. About a million people were without power in Puerto Rico after Irma sideswiped the island, but there were no immediate reports of large-scale casualties.

But the first islands hit by the storm were scenes of terrible destruction.

French Prime Minister Edouard Philippe said four people were confirmed dead and about 50 injured on the French side of St. Martin, an island split between Dutch and French control. The toll could rise because rescue teams had yet to get a complete look at the damage.

Three more deaths were reported on the British island of Anguilla, independent Barbuda and the Dutch side of St. Martin.

Irma also slammed the French island of St. Barts, tearing off roofs and knocking out electricity.

French Interior Minister Gerard Collomb said 100,000 food rations were sent to St. Barts and St. Martin, the equivalent of four days of supplies.

“It’s a tragedy. We’ll need to rebuild both islands,” he said. “Most of the schools have been destroyed.”

Photos and video of St. Martin circulating on social media showed major damage to the Philipsburg airport and heavy flooding in the coastal village of Marigot.

Dutch Prime Minister Mark Rutte said the storm “caused wide-scale destruction of infrastructure, houses and businesses.”

“There is no power, no gasoline, no running water. Houses are under water, cars are floating through the streets, inhabitants are sitting in the dark in ruined houses and are cut off from the outside world,” he said.

Far out in the Atlantic, Hurricane Jose grew into a Category 2 storm, threatening some of the same islands ravaged by Irma.

Meanwhile, Irma, the most potent Atlantic Ocean hurricane ever recorded, appeared increasingly likely to rip into heavily populated South Florida early Sunday.

People rushed to board up their homes, take their boats out of the water and gas up their cars. With gasoline running out and tensions rising, the Florida Highway Patrol escorted tanker trucks sent to replenish gas stations.

“It is wider than our entire state and could cause major and life-threatening impacts from coast to coast. Regardless of which coast you live on, be prepared to evacuate,” Gov. Rick Scott said.

Brian McNoldy, a hurricane researcher at the University of Miami, said Irma could easily prove to be the costliest storm in U.S. history.

French President Emmanuel Macron’s office said he would go to the islands as soon as the weather permits it. Saying he was “grief-stricken,” Macron called for concerted efforts to tackle global warming to prevent similar natural disasters.