By Victoria Craw and Debra Killalea

Hurricane Irma has taken a deadly turn, and two other storms in the Atlantic are set to add to the destruction.

The first deaths from Hurricane Irma have been reported as the Category 5 storm tore through the Caribbean.

CNN and the New York Times are reporting two people have been killed.

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A tropical storm in the Atlantic and another in the Gulf of Mexico were upgraded to hurricane status today, the US National Hurricane Centre confirmed.

Hurricane Jose was 1675km east of the Lesser Antilles in the Atlantic and packing maximum sustained winds of 120km/h, the NHC said.

It was considered a Category 1 hurricane on the five-level Saffir-Simpson scale.

The NHC said tropical storm Katia in the southwest Gulf of Mexico had also become a Category 1 hurricane.

It said a hurricane watch was in effect for the coast of the Mexican state of Veracruz where heavy rainfall could be expected.

Hurricane Irma has roared through Caribbean islands with historic 297km/h winds on its way to a possibly devastating hit on Florida.

Winds gusting up to 354km/h have pounded the region for 24 hours.

Footage on social media showed homes underwater and strong winds whipping islands.

The strongest Atlantic Ocean hurricane ever measured destroyed homes and flooded streets across a chain of small islands in the northern Caribbean, passing directly over Barbuda and leaving the island of about 1700 people virtually incommunicado.

Later, Barbuda and Antigua Prime Minister Gaston Browne said the storm had destroyed 90 per cent of the structures on the island. "As it stands, Barbuda is practically uninhabitable," he said.

• READ MORE: Kiwi in Florida - 'It's barrelling straight toward us'

This is only the second time since satellites started tracking storms about 40 years ago that one has maintained 185km/h winds for more than 24 hours, said Colorado State University meteorology professor Phil Klotzbach.

The other was the massive killer typhoon Haiyan that killed more than 6000 people in the Philippines in 2013.

"It's a humdinger," he said.

"This thing is a buzzsaw; I'm glad Floridians are taking it very seriously," Klotzbach said. "This is going to be a bad storm. I don't see any way out of it."

The French Minister for Overseas Territories confirmed two fatalities as the hurricane charted a course towards Puerto Rico and Florida.

The two dead are from France's Caribbean territories, St Martin and St Barthelemy.

French President Emmanuel Macron said that it was too early to come up with a final toll from the rare Category 5 storm, but it would be "harsh and cruel".

Deadly, devastating Irma

Irma is threatening millions of people in the Caribbean and Florida.

Sky News weather chief meteorologist Tom Saunders said Harvey was destructive, but Irma is packing a bigger punch.

Dangerous storm surges and record-breaking winds were adding to Irma's destructive impact.

"The winds are much more powerful than with Harvey," Saunders said.

"With mean winds of 295km/h and wind gusts to 360 km/h it's certainly up there for the strongest on record."

Irma is the equal strongest storm since Allen in 1980, which killed 269.

Saunders said hurricanes form over water and dissipate once they hit land.

"The warmer the ocean the more energy is available for a tropical cyclone to form," he said.

Saunders said Irma has more room to grow but Harvey produced more rain because it was moving slower.

"Harvey was a Category 4 so less strong winds (209km/h) but slower in duration and therefore produced more rain," he said.

However storm surges are expected to be 6m with Irma, which Saunders said would add to the destruction.

Category 5 winds had the potential to uproot trees, signs and tear roofs off homes.

Buildings could also be destroyed while mass evacuations and low escape routes being cut off are also expected under a storm system this strong.

"It's catastrophic damage," he said.

"This storm system is expected to bring storm surges up to 6m to some low-lying areas of the Caribbean," Saunders said.

Irma's strength is partly due to the fact that water in the area is 1-1.8C warmer than normal.

Saunders said three hurricanes was not uncommon for this time of year, which was peak hurricane season.

Irma is just one of three hurricanes in the Atlantic along with Katia and Jose. The last time this happened was seven years ago, according to CNN.

If Irma hits Florida as a Category 4 or 5 storm, it will be the first time in history that the US was hit by two Category 4 or 5 storms in one year, Associated Press reported.

Forecasters warn Irma could strike the Miami area by early Sunday US time before raking the entire length of the state's east coast and pushing into Georgia and the Carolinas.

AP science writer Seth Borenstein, who has covered hurricanes for 25 years, said Irma was a much more dangerous storm than Harvey.

"Irma is moving and is moving quickly but it's much stronger so the issues are going to be storm surge, wind and rainfall," he said.

Meanwhile multimillion-dollar homes belonging to Johnny Depp, Donald Trump and Oprah Winfrey are under threat from destructive Irma.

'Potentially catastrophic'

The killer storm is so powerful it has registered as seismic activity on some instruments and packs more power than this year's previous eight storms combined, according to a US scientist.

The NHC warned the "potentially catastrophic" hurricane will bring "life-threatening wind, storm surge and rainfall hazards" to the Virgin Islands and Puerto Rico.

Emergency warnings were in effect across the Bahamas, Dominican Republic, Turks and Caicos. Cuba and Florida are likely to be hit later in the week.

Ahead of the storm

• The Governor of the British Virgin Islands ordered a 36-hour curfew for residents.
• Emergency evacuations were ordered for six islands in the Bahamas and are expected in the Florida Keys.
• The White House declared a state of emergency in Florida, the US Virgin Islands and Puerto Rico.
• President Trump said it "looks like it could be something that will be not good. Believe me, not good."
Billionaire Richard Branson was holed up on his private home on Necker Island.
• Hotels issued warnings to guests who described "apocalyptic" noises.
• Storm surges six metres above normal tide levels are expected.
• Puerto Rico residents prepare to be without electricity for four-six months.
• Colorado State University professor Phil Klotzbach warns "the Leeward Islands are going to get destroyed."
• Tropical storm Jose is expected to become a hurricane in 36-48 hours.

'May God protect us all'

The Red Cross said it is bracing for a "major humanitarian response" to the storm made worse by the severe rainfall and isolation of the islands.

The agency's regional director Walter Cottee said: "We are anticipating major impacts on a number of islands, and we are preparing to respond to needs that may arise."

"One of the main challenges is going to be logistical, given the isolation of some the islands. We need to ensure a reliable channel for relief efforts in the aftermath of the hurricane."

France's minister for overseas territories, Annick Girardin, said the office had likely underestimated the storm's power as it hurtled towards the French-run territory of St Barths. It has already "blown the roofs" off buildings and is expected to hit the larger French islands of Guadeloupe and Martinique.

Antigua resident Kazia phoned a local radio station to say she was "praying to God" while being hunkered down with no power. Visitors to the island were turned away from the closed airport on Tuesday with the words: "May God protect us all."

London PR expert Alex Woolfall, who specialises in crisis management, tweeted that he could hear "thunderous sonic boom noises outside" from his hotel in St Martin.

Care Australia's emergency teams said they were working to prepare clean drinking water, food supplies and shelter for residents in Haiti which is still recovering from Hurricane Matthew one year ago.

Country director Karl Paul said it could be a "monster" storm when Irma hits on Thursday.

"Irma's biggest threat is flooding and mudslides in addition to damage from the hurricane's heavy winds and rain. We're also concerned the anticipated flooding could contaminate the water supplies," he said.

Video and images posted on social media show the strength of the storm as it moves across the Caribbean and towards the Gulf of Mexico.

People board up windows in preparation for Hurricane Irma, in Canovanas, Puerto Rico. Photo / AP
People board up windows in preparation for Hurricane Irma, in Canovanas, Puerto Rico. Photo / AP
Shoppers wait in line for the arrival of a shipment of water during preparations for the impending arrival of Hurricane Irma in Altamonte Springs, Fla. Photo / AP
Shoppers wait in line for the arrival of a shipment of water during preparations for the impending arrival of Hurricane Irma in Altamonte Springs, Fla. Photo / AP

More than 100 Kiwis in path of Irma

More than 100 New Zealanders are in the firing line of the monstrous Hurricane Irma, authorities say.

The Ministry of Foreign Affairs and Trade said 110 Kiwis are known to be in the path of the Category 5 storm - the biggest hurricane ever recorded in the Atlantic.

"New Zealanders currently in the path of Hurricane Irma are advised to follow any instructions issued by the local authorities, including any evacuation orders, keep their family in New Zealand informed of their well-being and contact their airline or travel agent directly if their travel has been disrupted," an MFAT spokesman said.

The 110 New Zealanders are those that have registered with the Government's SafeTravel website, he said.