A mugger who attacked a woman in Japan fled empty-handed -- and with one finger missing -- after the intended victim chomped off his pinkie.

The 59-year-old woman fought back after a man snatched her bag as she arrived at her apartment in the northern city of Sapporo, police said Tuesday.

The woman gave chase as her attacker made his getaway on a bike, wrenching the stolen tote from his grasp and biting down firmly on his little finger.

"The victim regained her bag in a scuffle and the suspect had one of his fingers partially bitten off before getting away on his bicycle," a local police spokesman told AFP.

Local media reported the top third of the man's finger, which the woman said was from his right hand, had been recovered from the crime scene.

A police spokesman refused to give details about the fate of the detached digit or whether prints had been taken in a bid to trace the attacker.

The removal of the upper part of the little finger is a traditional form of penance for members of Japan's yakuza organised crime gangs.

There is no suggestion that the alleged attacker was a mobster, who usually use a sharp knife -- rather than teeth -- and perform the amputation personally.