A schoolgirl and a 39-year-old man were killed and 15 other young girls injured when a knifeman attacked a group of children waiting for a bus to primary school outside Tokyo on Tuesday.

The apparently random attack took place in the city of Kawasaki, just south of the capital, as the children waited with their parents at a bus stop at about 7.45am.

The suspect, a man in his 50s, was detained at the scene and later died from self-inflicted injuries to his shoulder and neck, national broadcaster NHK reported.

Kiyoshi Matsuda, deputy director of the Nippon Medical School Musashi Kosugi Hospital, told reporters that the 11-year-old schoolgirl and a 39-year-old man had succumbed to their injuries.

Hanako Kuribayashi, who was in the sixth grade, and foreign ministry official Satoshi Oyama, who is believed to be the parent of another child, both died, police said later.

Another woman was severely injured along with the 15 other schoolgirls who were hurt, NHK said.

Eyewitnesses report seeing the man, described as being in his 40s or 50s, stabbing the girls with knives in both hands as they waited in line for their school bus.

The girls, aged between 6 and 12, were students at a private Catholic school.