Police have detained a teacher in East China's Shandong province on suspicion of beating a student to death with a stick and injuring three others, Beijing News reported on Sunday.

The 50-year-old woman, identified only as Li, had been leading an after-school tutorial class at her home in Wulian county when the incident happened on Saturday.

He Zhaolong, the father of the student who died, told Beijing News that the teacher lived in their neighborhood and that his son, 12, had been taking her classes for several years.

He said his son had been beaten on the head and died due to a severe injury. He added that there were about a dozen students at Li's home at the time of the alleged attack.

"She was giving classes on Saturday morning when she suddenly locked the door and started beating the children with a big stick until some of the children escaped and found help," He was quoted as saying.

A photo circulated online over the weekend reportedly showed his son covered in blood.

He said he did not know what may have prompted the attack, adding that his family had no previous conflicts with Li.

The local authorities said the suspect used to be a substitute teacher in her village but was dismissed in 2002. Since then, she has made a living by running tutorial classes at her home, teaching Chinese language and math to students in third to sixth grade.

In a statement released online, Wulian police said a thorough investigation is underway, while many netizens expressed their outrage at the incident and their sympathy for the victims' families.

The alleged attack is the latest violent incident involving Shandong teachers this month.

On May 23, a teacher at a junior middle school in Dezhou was sacked and ordered to apologize after slapping a student in the face.

On the same day, a kindergarten teacher in Yantai was dismissed after being accused of beating a 5-year-old child.

According to guidelines issued by the Ministry of Education in 2014, teachers who use physical punishments on students should receive penalties ranging from a warning to instant dismissal.