A man alleged to be mentally ill stabbed eight school children to death and injured five others on Tuesday in Fujian province, a tragedy which experts said once again points to inadequacies in the treatment of such people.

Parents are overwhelmed with shock and grief at a local hospital after a knife-wielding man attacked their children at Nanping City Experimental Elementary school Tuesday morning. [China News Service]

Police arrested the man identified as Zheng Mingsheng, a former community doctor in Nanping city, according to Huang Zhongping, spokesman for the city's public security bureau.

Zheng, born in 1968, is a native of Nanping and used to work at the Mazhan community clinic before he resigned in June 2009, Huang said.

Zheng is said to have a history of mental illness, and local reports said he was fired by the community clinic for mental health problems.

"Sometimes he acted abnormally but we never imagined he would do such a cruel thing," a community resident said.

The attack happened at 7:20 am at the entrance of Nanping Experimental Primary School.

Zheng charged into a group of students wielding a 25-cm knife, witness Gan Guiping, the school's PE instructor, told China Daily.

"They don't allow me to live and drive me crazy. I will not spare them," Gan recalled Zheng as shouting repeatedly.

He said the attack lasted less than a minute, and three died at the scene.

"After being stabbed, some of the students rose, stumbled a few steps and then fell," Gan said with tears in his eyes.

"I saw them die in front of me."

Cai Luyan, director of the school's moral education section, said the attack took the students by total surprise.

"A boy in Grade 1 was stabbed to death in front of his mother," Cai said.

Zheng was subdued by passers-by and school security guards, said Wu Jiachong, owner of a store who called the police.

The school, which has 2,000 students, was closed for the day and the students were taken home by their families, Xinhua News Agency reported.

"My mind went blank when my son's teacher called me at 8 am, saying he had been stabbed," said Lu Yanping, mother of 12-year-old Liu Luyi, at the intensive care unit of Nanping People's Hospital

"He is still in critical condition."