The trio used a hammer to dismember Kazuyuki Kobayashi, before grilling parts of his body and getting rid of it in mountains in rural Japan, a police spokesman told AFP.

Broadcaster TV Asahi said two of the men had confessed to killing Kobayashi and stewing some of his flesh in a curry, in an effort to hide the smell.

Tasuku Shimaoka, 34, Keita Yoshida, 30, and Koji Kawamura, 40, were arrested last week on charges of dismembering Kobayashi, who had been missing for around three years, the police spokesman said.

It is common for Japanese police to arrest suspects on lesser charges initially in order to extend the time they are allowed to keep them in custody.

Media reported Kobayashi's body had been stored in a warehouse refrigerator in Tokyo before being taken to Niigata in the country's north.

"The suspects conspired between July and August of 2011 and used a hammer-like object to destroy (Kobayashi's body). They then cooked the flesh on a barbecue grill," the spokesman said.

"They damaged and dumped the remains in mountains," he said, without elaborating further.

Local reports said there was some kind of money trouble among the men.

Yoshida has admitted all charges against him, Kawamura has confessed to some, while Shimaoka is maintaining his innocence, the police spokesman said.