SYDNEY (AFP) - A British backpacker was missing in Australia's remote Outback on Thursday after failing to return from a hike, sparking a police search with fears he may have come to harm.

The 18-year-old was last seen on Tuesday evening when he set off from the Upshot Station homestead, about 130 km from the far-flung Queensland town of Longreach, some 700 km inland from the coast.

Police launched a land and air search, fearing for the man's safety due to his lack of familiarity with the property, which sprawls across 1,300 hectares.

"Lack of water, the heat, venomous snakes and injury are probably our greatest concern," Sergeant Dave Perry told the Australian Broadcasting Corporation.

He said the missing man was apparently hoping to enter the armed forces once back in Britain and had some survival training.

"He may have been using some of the rougher country and the jump-ups to improve his fitness," said Sgt Perry.

Planes, motorbikes, and four-wheel drives were being used in the search, with neighbours also combing the area on foot and horseback and an emergency services helicopter dispatched with medical staff.