A Laotian man has told police he murdered his pregnant wife with an axe because he wanted the foetus to make a lucky charm which might help him win the lottery, a report said.

The 38-year-old was arrested a day after allegedly luring his wife, aged 24, into the forest of north-eastern Xieng Khuang province on January 3 and killing her with an axe blow to the back, the Vientiane Times reported.

It said the foetus had not been found.

Police told the state-linked newspaper that the man confessed he planned to use the three-month old foetus to produce a "louk lord", a mystical object which, according to local legend, can give its owner great power and fortune.

"The murderer confessed to the terrible crime, but he won't explain where the body of his unborn child is," Major Khamsouk Phonkhamdy, chief provincial police investigator, was quoted as saying.

The suspect said he had heard that if he "produced a 'louk lord' he would be able to ask the ghosts for lucky lottery numbers," Major Khamsouk added.

"Or he could sell the 'louk lord' at an extremely high price."

The investigator reportedly said it was unclear whether the killer worked alone or had accomplices who were still trying to produce the "louk lord".

Laos is one of Asia's poorest countries. While most people are Buddhists, belief in spirits remains widespread.

- AFP