A nudist suffered burns to one-fifth of his body after he tried to set a spider on fire while naked in a resort near the Australian city of Bowral, near Sydney.

An ambulance service spokesperson said, the 56-year-old victim tried to kill what he thought was a deadly funnel web spider by pouring gasoline down the spider's burrow and lighting it with a match.

The gasoline ignited and a searing burst of flame engulfed his bare legs and buttocks.

He was flown by helicopter to a Sydney burn unit.

A statement from the hospital says, "The fate of the bunkered spider was unknown, although other guests at the resort thought it was probably a harmless trapdoor spider and not a deadly funnel web."

Fellow nudists tell Australia's AAP news agency that, rather than a funnel web, the insect he was afraid of was a harmless trapdoor spider.