Police in Kurashiki, Okayama Prefecture, said Saturday that at least 30 elementary schools received postcards this week, in which the sender threatened to kidnap a child.
According to police, the postcards arrived on Aug 27 and 28. Fuji TV reported that police increased patrols around the elementary schools on Friday, while parents were alerted not to let their children walk to and from school alone.
Police said the postcards were sent from Kanto post offices.
In July, an 11-year-old girl was kidnapped while on her way home from school in Kurashiki and kept confined for six days before being rescued unharmed from the house of her kidnapper.
Feature image via Chiebukuro