(AFP) - Residents on France's Reunion Island were confined to their homes early Monday, as the authorities issued the highest alert for what they said could become a devastating tropical storm.

The Violet-Level alert, which comes into force at 6:00 am (0200 GMT) means all people on the island, including the emergency services, should observe a strick lockdown.

"All circulation is formally prohibited for any reason whatsoever, and until further notice," the official statement added.

Authorities urged residents of the island in the Indian Ocean to stock up on food and water and stay indoors for 36 hours.

Many balconies and gardens had been cleared of any objects that could be carried away or broken, and shopkeepers took in removable signs.

The tropical storm, dubbed Belal, which by Sunday afternoon was 200 kilometres north-west of Reunion, could become an "intense tropical cyclone" Monday as it passes over the island or its immediate vicinity.

French President Emmanuel Macron took to social media on Sunday to urge the island's 870,000 residents to stay indoors. "Be careful, stay at home," he said on X.

The last major cyclone to hit Reunion was in 2014.

But speaking about the dangers of the current storm, authorities evoked Jenny, a deadly cyclone that battered Reunion in 1962.

- 'Devastating winds' -

"We are not going to play heroes, we were told to stay at home," said Jules Dafreville, who lives in the capital Saint-Denis.

"I returned in the middle of the afternoon and I don't plan to come out before the red alert is lifted on Tuesday morning."

The island's main airport said it was suspending flight operations.

The Meteo France weather service warned that winds could exceed 200 km/h on the coast and 250 km/h or more in the highlands.

"These are destructive and devastating winds that could cause major damage", said Sebastien Langlade, head of forecasting at Meteo France Reunion.

Six emergency health centres were set up for people requiring treatment, in addition to the 142 accommodation centres across the country for people to use in the event of flooding.

Olivier Blondet, manager of two restaurants and a nightclub in Saint-Denis, prepared his three establishments for the worst.

He fixed the sofa on his terrace to the railings and removed blunt objects, he said.

"We're trying to make sure there's absolutely nothing that can come off the ground and be thrown onto the windows or walls," he said on BFMTV.

In Saint-Denis, around twenty homeless people were taken to a shelter.

© Agence France-Presse