Beijing (AsiaNews/Agencies) – A man with a knife killed eight people and injured four others at a high school Friday, in the deadliest of a series of knife attacks at Chinese schools in recent months, the government said.

Police were searching for the attacker following the killings at the No. 2 High School in the city of Ruzhou, the official Xinhua News Agency said.

A woman who answered the phone at the school in central China said the injured were hospitalized and gave more details about the killing: "It happened in the boys dormitory. It happened around midnight" the woman said, but she wouldn't give her name or other information. No one was available for comment at the police headquarters.

It was the fourth knife attack reported since August at a Chinese school or day care center. The earlier assaults left one child dead and a total of 42 people injured. The reason for the surge in knife assaults isn't clear. Henan is among the poorest provinces in China.

The spate of violence prompted the government of President Hu Jintao to issue a nationwide order in September for schools to hire guards and tighten security. Newspapers in Beijing say schools in the Chinese capital have begun to post guards, but it wasn't clear whether any additional security was in place at the school in Ruzhou.

On Wednesday, a court executed a man who slashed 25 children with a kitchen knife in September at a grade school in eastern China. Though no one was killed, a court ruled that the penalty was justified because the violence was "especially cruel."

In August, a man with a history of schizophrenia killed a student and slashed 14 children and three teachers at a Beijing kindergarten near the compound where China's leaders live and work. In September, a man armed with a knife, gasoline and homemade explosives broke into a day-care center in the eastern city of Suzhou and slashed 28 children before police stopped him. Police haven't disclosed a possible motive.