A hammer-wielding man wounded 20 children in an attack at an elementary school in Beijing Tuesday with three suffering serious injuries, local authorities said.
A male suspect was brought "under control" and the wounded pupils were admitted to hospital, the Xicheng district government said.
Surnamed Jia, the 49-year-old assailant was a contractor hired by the school for daily maintenance work.
His contract was scheduled to terminate at the end of January, stated the district government on its official Twitter-like Weibo account in a post that has since been deleted.
Though the school was discussing another job posting for Jia, he used a hammer and attacked students to "vent his resentment", they said.
Police have taken "compulsory measures" against the suspect.
Beijing police did not immediately respond to AFP's request for comment.