were aged between six and 12 years old, were students at a private Catholic school and were waiting with their parents at a bus stop at around 7.45am.

Image: A knife-wielding man reportedly screamed 'I will kill you' before attacking commuters

Three of those injured were said to be in a serious condition, while the injuries of the other pupils were not thought to be life-threatening.

Police recovered two knives at the scene. The suspect's identify and motive for the attack are still unknown.

Witness Yasuko Atsukata said: "I heard a scream so I stopped and turned around to see what happened. It was not a normal tone of voice."

She added she saw a person collapse shortly before a second person also fell. "The colour of their white shirts turned red afterthey collapsed, then I understood they got stabbed."

One witness told NHK: "I heard screaming, then I saw a man standing with a knife in each hand. Then he crumbled to the ground."

Another told the Asahi newspaper the too saw the man shouting and around eight children on the ground near him.

Citing the police, NHK reported that a bus driver told officials that a man holding a knife in each hand walked toward the bus and started attacking the children.

Television footage showed emergency workers giving first aid to people inside an orange tent set up near the scene, and police and other officials carrying the injured to ambulances.

Image: Thirteen schoolgirls were hurt in the attack

Prime Minister Shinzo Abe said the attack was "extremely harrowing" and vowed to step up