Falconio was killed while travelling in the Northern Territory with his girlfriend Joanne Lees in 2001 but his body has never been found

Northern Territory police are offering a $500,000 reward for information on the location of the remains of British backpacker Peter Falconio, whose murder in the Australian outback more than 20 years ago captured worldwide attention.

In July 2001, Falconio, then 28, was travelling Australia with his girlfriend, Joanne Lees, on a remote stretch of highway about 300km north of Alice Springs in the Northern Territory when he was pulled over by Bradley John Murdoch, who said their van might have an engine problem.

Falconio went behind the car with Murdoch to investigate, and Lees heard a gunshot, before Murdoch cable-tied her and covered her head.

Lees managed to escape and hide in bushland for five hours while pursued by Murdoch and his dog before flagging down a truck driver, while Falconio died from a gunshot wound to the head.