Japanese police arrested a man after they said he ploughed his car deliberately into seven primary school children in the western city of Osaka on Thursday.

The children, who had been on their way home from school, were injured and rushed to hospital but all seven remained conscious.

An Osaka police official, who declined to be identified, said the driver was a 28-year-old man who lives in Tokyo.

"I was fed up with everything, so I decided to kill people by ramming the car I was driving into several elementary school children," the official quoted the man as saying.

Police are holding him on suspicion of attempted murder, the official said.

The children are aged seven and eight and police said the most serious injury was a fractured jaw suffered by a seven-year-old girl.

The other six, all boys, appeared to have suffered comparatively milder injuries that included bruises and scratches and they were under examination, police said.

The car was "zigzagging" as it hit the children, with one girl "covered in blood and other kids suffering what appeared to be scratches", a witness told Nippon TV.

The driver was wearing a surgical mask and "looked like he was in shock" after he was dragged out of the car by school teachers, Nippon TV quoted a witness as saying. (AFP)