He said two of the children had avoided involvement in the attack and escaped injury. Police believe a length of wood or long stick had been used to beat the other two.
Mr Lee said a 17-year-old youth had been arrested and was being held in custody to appear in Masterton District Court today, charged with assault with a weapon.
The children had been referred to Child, Youth and Family, Mr Lee said, independently of the assault charge and investigation.
"That children of that age were out in the street at such a late hour was very concerning."
He said police were still investigating whether there were others involved in the attack on the children and if further arrests were possible.
In the unrelated matter involving the attempted motorcycle theft, Mr Lee said the alleged offender had been arrested at an Intermediate St property, about 1km from Pownall St, where the foot chase had began.
He said the resident had received minor injuries in the assault.
Mr Lee said the officers had entered the Intermediate St property using the new Search and Surveillance Act that came into effect on October 1.