A former doctor armed with a large knife killed eight children and injured five others Tuesday at an elementary school in eastern China, a local official said.

The assailant was arrested after the 7:20 a.m. attack, Xinhua News Agency said. He is a former community clinic doctor with a history of mental health problems, said a man surnamed Wu in the Nanping city government office, who would not give his full name as is common among Chinese officials.

Eight children from Nanping City Experimental Elementary School were killed, and five were being treated at a hospital, Wu said. Six died at the scene.

The attacker, who is 41 or 42, had resigned from his post at the community clinic, Wu said, but he wasn't sure when.

The school, located in Fujian province, was closed and students were sent home.

China has witnessed a series of school attacks over the past several years, which are often blamed on personal grudges or people with psychiatric problems, leading to calls for improved security.