A Japanese father has called for his own son to hang after a gruesome murder spree in which the teenager killed three family members before slashing open his mother's belly and putting a doll inside.

The father says he will seek the death penalty for his 18-year-old son, who is a fan of the grisly Hannibal Lecter novels and has written horror stories himself.

"The only solace is he didn't kill people outside the family," he told Thursday's edition of the the Shukan Bunshun weekly magazine.

"I'm grateful some people advised me to get him an excellent lawyer, but I hope to see an early ruling," he said.

"I want him to get the death penalty - that's my honest feeling now."

The teenager, who cannot be identified because of his age, has admitted stabbing to death his mother, brother and sister with a large survival knife on January 9, a police official said.

He then reportedly cut open his mother's belly and put a doll inside before torching the family's apartment in the northern town of Hachinohe.

The father says his son told him he was writing a novel about seven criminals who get together to destroy a town. One scene reportedly depicts a man stuffing a doll into his mother's body.

His 55-year-old father says he felt disgusted when he saw his son grinning in pictures taken after his arrest, and wanted him to hang.

"I will make it clear in court. I don't know how he'd feel about it. But I want to tell him I'll pick up his bones for sure," he said.

In Japan, relatives traditionally take the bones of a cremated body in an urn for burial.

The father, who divorced the boy's mother a decade ago and has been in and out of prison on blackmail charges, admitted he was partly responsible for his son's poor upbringing.

He said while he was in prison, his son sent him the Hannibal Lecter novels by Thomas Harris about the psychiatrist turned cannibal serial killer portrayed by Anthony Hopkins in Silence of the Lambs and Hannibal.

-AFP