Tuesday's stabbing rampage in Sagamihara, Kanagawa Prefecture, has highlighted the difficulty of reigning in crimes involving knives, despite a recent revision to the Firearm and Sword Control Law.

Knives have often been the weapon of choice in single-perpetrator mass murders in Japan, where gun ownership is strictly prohibited.

In 2009, the government revised the law to effectively ban the possession of daggers and other doubled-edged knives with blades 5.5 cm or longer, in the wake of the indiscriminate stabbing of pedestrians the previous year in Tokyo's Akihabara district.

In that incident, 25-year-old Tomohiro Kato rammed a truck into a street crowd, running people over and then going on a stabbing rampage, killing a total of seven.

Before the 2009 revision, the law banned swords, knives and spears with blades 15 cm or longer. In the Akihabara attack, Kato used a 13-cm dagger.

Violators of the revised law face up to a three-year prison term and maximum ¥500,000 fine.

It is not yet known what kind of knives Satoshi Uematsu, the alleged perpetrator of the Sagamihara stabbings, used when he attacked residents at Tsukui Yamayuri En, a care facility for people with mental and physical disabilities, in the early hours of Tuesday.

Uematsu is reported to have been in possession of three knives, including a Japanese-style kitchen knife, when he turned himself in to local police shortly after the rampage.