Fearing that his reclusive son might cause the public harm, a former top bureaucrat in ­Japan stabbed the 44-year-old to death, domestic media said, days after a mass stabbing by another recluse shook the ­nation.

The incidents spotlight Japan's growing legion of adult hikikomori, as they are known, people who live at home with their parents and seldom, if ever, venture out, spending their days in hermit-like seclusion.

Tokyo metropolitan police said they arrested Hideaki Kumazawa, 76, on Saturday for attempted murder for allegedly stabbing his son with a knife. On Monday, media said he was now a murder suspect after the man died.

National broadcaster NHK said Kumazawa, a former ­envoy to the Czech Republic, told investigators his alarm over his son was provoked by news last week of a knife-­wielding man who slashed at a group of schoolgirls, killing two and injuring 17. The suspect in that incident was also middle-aged and rarely left the house where he lived with his elderly aunt and uncle. He killed himself soon after the stabbings.

Kumazawa told police his son had been a recluse and sometimes violent, NHK said. The stabbing followed an argument in which he scolded his son for getting angry at the noise generated by a sports event at a nearby school, media said.

Once stereotyped as video game-playing young men, Japan's recluses are aging, and those aged from 40 to 64 ­number more than 610,000, the cabinet office said in a survey released in March.