A KNIFE-wielding man killed seven middle schoolchildren and injured 12 others as they returned home in northern China on Friday, in one of the deadliest such rampages in the country in recent years, authorities said.

The suspect was detained and the injured children were receiving hospital treatment, the propaganda department of Mizhi County in Shaanxi province said on its official social media account.

The incident took place at around 6:10pm local time, the department said, without providing further details.

7 children died, another 12 injured after being attacked after school in Mizhi, NW China's #Shaanxi province on Friday; The suspect has been detained and the injured are receiving treatment at hospital, the local government said pic.twitter.com/ap3VYiDMBL — People's Daily,China (@PDChina) April 27, 2018

According to the BBC, Chinese police say his given surname is Zhao and he is a 28-year-old former student at the school.

He reportedly committed the crime because he was bullied in his third year.

The ages of the children were not given, but middle schooners are usually between 12 and 15 years old in China.

The injured children are receiving treatment in hospital.

A local police official said that the case was under investigation and declined to provide more details.

It’s not the first time a school knife attack has made headlines in China.

A series of uncoordinated mass stabbings took place across the country from 2010-12, with the Associated Press noting “attackers often seek out the vulnerable, hoping to amplify their outrage before they themselves often commit suicide”.

— with wires