Bangkok: Authorities on Tuesday urged visitors to the popular Thai resort island of Koh Phangan to take care when swimming after a five-year-old French boy died from a sting by the world’s most toxic jellyfish.

The boy, who was holidaying with his family, died on Saturday evening after he was stung by a box jellyfish — regarded as one of the deadliest creatures on earth.

While stings from the species are rare, they are potentially fatal, prompting police on Koh Phangan to urge hotels and local authorities to warn tourists to be careful in the water.

“Preliminary tests found the boy died of a box jellyfish sting,” Police Lieutenant Saengroj Somrotrat told AFP, adding his body was awaiting repatriation to France.

“We have asked them [hotels and resorts] to help warn people and prepare emergency kits if people come into contact with the jellyfish,” he said.

Phangan, in the Gulf of Thailand near Koh Samui, is home to the hedonistic full-moon beach party, which draws hordes of mainly young backpackers from across the world.

The box jellyfish has trailing tentacles two to three metres (6.5 to 10 feet) long that can pack a lethal sting for swimmers. It feeds on small fish and crustaceans.

Saengroj said the season for box jellyfish will run until the end of October.