TOKYO (AFP) - A court has jailed a 22-year-old Japanese man for killing a Nepalese restaurateur in an unprovoked street attack in which the victim was repeatedly kicked as he lay unconscious on the ground, reports said.

The court in the western city of Osaka on Monday found tattoo artist Hiroki Shiraishi and his female acquaintance Miyoko Shiraishi, 23, guilty of causing the death of 42-year-old immigrant Bishnu Prasad Dhamala last year.

Hiroki Shiraishi was jailed for 19 years, and Miyoko Shiraishi was ordered to serve nine years. It was not known if the two were related.

The duo were heavily drunk before they began what the court said was a random assault on the street.

During the trial, security camera footage showed the Nepalese man collapse to the ground after being hit. His motionless body was then repeatedly kicked, Kyodo News reported.

The agency quoted judge Hidenori Nagai saying the pair "assaulted for fun without any reason a man who did not resist. It should never be condoned".

Violent crime is relatively rare in Japan and the country's small immigrant population is not routinely targeted in racist attacks.