Elementary schools nationwide reported to police last year 22 intrusions in which the intruders actually harmed pupils or had been likely to do so, the National Police Agency said Thursday.
Suspects were arrested in 18 cases, including one case of attempted murder, six cases of assault, three cases of indecent exposure or assault, three weapons violations and five unlawful entries, according to the NPA. Nine of the intruders were armed.
Of the 22 schools that experienced intrusions, 11 had not locked their gates and three did not have a fence surrounding the schoolyard.
School intrusions became a major concern after a man charged into Ikeda Elementary School in Osaka Prefecture in 2001 and fatally stabbed eight pupils.
The massacre prompted the NPA to strengthen school security in cooperation with the education ministry.
But the issue gained national attention again in December, when an intruder entered a Kyoto elementary school that had three unlocked gates and a security alarm switched off, and wounded two students.