People with mental health problems have been cited as a potential danger to public security after some recent crimes were allegedly committed by some who were suspected to be suffering from mental illnesses.

"We should get comprehensive information about people with high potential danger and keep a close eye on them to maintain social stability," Yang Huanning, vice-minister of Public Security, said recently, according to a transcript posted on Xinhua.net yesterday.

The remarks by Yang signal stricter supervision of people with severe mental illnesses, experts said.

"Severe mental illness does not make a person more violent, but people with such mental health problems would become incredibly cruel when committing crimes," Tian Chenghua, a doctor at the Institute for Psychiatric Research in Peking University's No 6 Hospital told China Daily, citing recent murders involving members of the family.

Zhang Wuli, 38, killed his wife and son on the morning of Dec 27 in a residential community in Daxing district, Beijing. Zhang was allegedly suffering from mental health problems.

On the night of Nov 23, Li Lei, 29, killed his wife, parents and two sons, a 7-year-old primary school student and a 1-year-old baby, also in Daxing.

Currently, around 170 million people in China suffer from mental health problems and nearly 16 million of them need medical treatment, statistics show.

Mental illness covers a wide range of problems, from depression to schizophrenia, accounting for 20 percent of all prevalent illnesses in the country. It has become a serious threat to public health, with the number expected to touch 25 percent by 2020, the Ministry of Health said.

Yang also urged the nation's police to increase supervision and curb crimes committed by mafia-style gangs, human traffickers, drug dealers and other criminals.

"We are facing all kinds of challenges and risks from home and abroad. We should take proactive measures to combat separatists, terrorists and extremists," Yang said.

He also called for a comprehensive security system covering both the real and virtual worlds to maintain social stability.