TOKYO (REUTERS) - A Japanese man was sentenced to life in prison on Wednesday (Dec 18) after a stabbing attack on a speeding bullet train in 2018 that left one dead and two others injured, sparking a national debate about safety as Tokyo prepares to host the 2020 Olympics.

Prosecutors had demanded the life sentence for Ichiro Kojima, 23, who said he had committed the crime on a Shinkansen train between Tokyo and Osaka out of frustration.

During Kojima's trial, Japanese media reported he had said spending life in prison "was a dream" he welcomed.

The knife attack set off widespread discussion in Japan on how to improve security on the country's network of bullet trains, known for both their speed and safety, as the country braces itself for a flood of visitors ahead of the Tokyo Summer Olympics next year.

Japan still has capital punishment, but prosecutors had stopped short of asking for the death penalty for Kojima, who was 21 when the attack took place.

Two women received knife wounds in the incident, while Kojima fatally stabbed Kotaro Umeda, 38, who tried to stop him.

In 2015, a man set himself on fire on one of the trains, killing himself and another passenger - an incident that prompted the installation of surveillance cameras on train carriages.

Kojima's attack prompted debate in Japan about how to improve security while still keeping trains running smoothly on very tight schedules and without inconveniencing passengers at crowded stations.

One rail firm, Central Japan Railway Co, placed security guards on all its Shinkansen trains.

Baggage inspections have so far been rejected due to concerns about inconveniencing passengers and slowing down train departures, but Japanese media has reported that research is ongoing into equipment that could scan baggage in seconds.