A man has been arrested after 20 children were attacked at a primary school in Beijing.
According to the post, three of the children had serious but non-life-threatening injuries.
All the injured children were receiving hospital treatment.
Some parents claimed on social media that around 20 children had been injured, although there were conflicting reports about whether a hammer or a knife had been used in the attack.
The man is a maintenance worker at the school and his contract is due to expire at the end of January, police said.
As an expression of his dissatisfaction, Xicheng district said, Jia wielded a hammer that he normally used for work to injure students during a class.
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The unnamed man is said to have targeted the youngsters around 11.15am local time at the school in the Xicheng district.
The attacker, originally from northeastern Heilongjiang province, had been detained by police and an investigation was under way, state television said.
"The details are still not clear", wrote one parent on WeChat. According to the school's website, it has 2,537 students and 199 teaching personnel.
It comes just months after a 39-year-old woman was reportedly held on suspicion of stabbing 14 school children in October last year in Chongqing.
In November, a driver rammed his auto into a group of children crossing a street in front of an elementary school in northeastern Liaoning province, killing five people and injuring at least 19.