An amorous triangle deep in the French countryside has come to a grisly end, prosecutors said Friday after arresting a man who shot his rival and buried him in a field.

The shooter, a farmer in his early 30s, confessed to the killing which he said was prompted by a rivalry for the love of a woman, said Etienne Manteaux, the prosecutor in the eastern city of Besancon.

Police investigated when the victim - 22-year-old Loan Bernede living in Cuisia, a village of barely 400 souls in the Jura region - went missing last month.

The suspect said he had found out that Bernede was sleeping with a woman that he, too, had a love relationship with.

He fetched a gun and shot his rival in the head with a .22 calibre bullet, Manteaux told reporters.

The suspect then dumped the body in a shallow grave he had shovelled out in a field on his farm.

Police at first interviewed him only as a witness, finding no reason to detain him.

But then he "panicked" and rushed to dig up and move the body, Manteaux said.

He carried it into an animal trough, poured 10 litres of petrol over it and set it on fire. After a blaze lasting seven hours, he probably discarded the ashes in a river, according to the prosecutor.

Police finally closed in when a witness came forward claiming "somebody close to him" had asked to borrow a van to move the body of a man he had killed.

This had happened in November, around the time that Bernede went missing.

After his confession, the farmer was charged with murder and incarcerated.

The murder weapon has not been found.