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Hundreds of tourists who have taken home a chunk of Australia's best-known landmark, the towering monolith called Uluru, have returned their illicit souvenirs, with some claiming to have been struck by bad luck as a result of the theft.

The national park that administers Uluru, formerly known as Ayers Rock, receives at least one package a day from people around the world, containing a piece of rock and an apology.

Jasmine Foxlee, who has been analysing the phenomenon, told the Australian newspaper The Sunday Telegraph that about a quarter of them believed they had been cursed for pocketing their souvenir.

They told stories that included marriage break-ups, family illnesses, and even deaths, which they attributed to their mementoes.

Others had belatedly realised Uluru's cultural and spiritual significance to the indigenous Australians who are its traditional owners, and wanted to return the chunks of rock to where they belonged.

About half a million tourists visit Uluru annually, and many of them climb the steep rock face, despite prominent signs explaining that they are trampling on ancient Aboriginal "dreaming" tracks.

Some, it seems, go further, and take a chunk of it home in their suitcases.

The largest rock sent back to date is a 32kg chunk - equivalent to the luggage allowance on most domestic flights - returned by a remorseful couple from South Australia. Another package containing a 9kg rock was posted from Germany.

Most purloined pieces are small enough to fit into a pocket.

Ms Foxlee, a PhD student at the University of Western Sydney, who has been studying parcels returned to the Uluru-Kata Tjuta National Park, said that most of them contained a note simply saying "sorry".

Others featured detailed stories of bad luck that had supposedly befallen people after their return home.

One British tourist explained: "Things were good in my life before I took some of Ayers Rock home with me, but since then my wife has had a stroke and things have worked out terribly for my children - we have had nothing but bad luck."

Ms Foxlee said: "When I went through all of those letters ... about 25 per cent made that reference to bad luck. Interestingly enough, a lot of the others were more about people wanting to see those rocks returned to their rightful place.

"There's quite a deep-seated uncertainty about Aboriginal spirituality and culture, and often we err on the side of caution when we don't know something well, so I think there's an element of, 'if I return it, it's a bit of a safeguard for myself'."