Women pray for the victims near the site of a knife attack in Kawasaki, near Tokyo, on May 29, 2019. File picture: Hiroki Yamauchi/Kyodo News via AP

Tokyo - A recent knife attack in Japan prompted a 76-year-old former top bureaucrat to murder his own son because he was deeply concerned that he could also inflict harm on others, local media reported on Monday.

Hideaki Kumazawa, who served as a top bureaucrat in the farm ministry, was arrested on Saturday for stabbing his 44-year-old son Eiichiro to death at their home in Tokyo, Kyodo News agency reported.

Kumazawa, who was also Japan's ambassador to the Czech Republic between 2005 and 2008, told police that he was motivated by his son's social withdrawal and domestic violence, Kyodo reported.

Kumazawa said his son "tended to be withdrawn from social life and showed violent behaviour" toward him and his wife, Kyodo reported, citing unnamed investigative sources.

The incident came less than a week after a knife-wielding man attacked two adults and 18 children at a school bus stop in the city of Kawasaki near Tokyo, leaving two people dead and one woman and 17 schoolgirls injured.

A school bus, centre, is parked at the scene of an attack in Kawasaki, near Tokyo, where a man wielding a knife attacked commuters waiting at a bus stop on May 28. File picture: Kyodo News via AP

The 51-year-old suspect in that attack, who stabbed himself in the neck and died in hospital, was also reportedly socially withdrawn or a "hikikomori" as they are known in Japanese. He had rarely left his home and lived with his uncle and aunt who were in their 80s.

The hikikomori phenonemon is one of the most serious social problems facing Japan.

An estimated 613 000 people aged between 40 and 64 are socially withdrawn, with job-related problems being the biggest reason for becoming recluses, according to a government survey published in March.