A knife-wielding man stabbed to death four primary school children in southern China on Friday, state media reported, the latest in a series of such attacks in recent years.

Three of the children died at the scene and the other was later pronounced dead in hospital, the official Xinhua news agency said, citing local authorities.

The stabbings occurred early in the morning as the children were on their way to school in the Guangxi Zhuang Autonomous Region, the report said.

It did not specify the children's ages or genders. The Beijing News daily, however, reported that none of the children were older than 12.

Police joined by members of the public were searching mountainous woodland for the suspected assailant, who police identified as a 56-year-old local man surnamed Shi, Xinhua said.

The report added that more than 300 people were participating in the manhunt along with sniffer dogs in an area about seven kilometres (four miles) from the site of the stabbings.

On its verified account on China's Twitter-like Sina Weibo, Chinese state TV described Shi as slightly heavyset and reported that he stabbed the children while riding a motorised trishaw.

Local police publicised the number plate of the trishaw and offered a reward of 20,000 yuan ($3,250) for information leading to the man's capture, it added.

Violent crime has been on the rise in China in recent decades as the nation's economy has boomed and the gap between rich and poor has expanded rapidly.

Studies have also described a rise in the prevalence of mental disorders, some of them linked to stress as the pace of life becomes faster and support systems wither.

In early September, state media reported that a man stabbed three children and a teacher to death and wounded several others in a rampage at a primary school that refused to enrol his daughter.

That followed a March 2013 incident in which a man killed two relatives and then slashed 11 people, including six children, outside a school in China's commercial hub Shanghai.

2010 alone saw five attacks that killed 17 people -- 15 of them children -- and wounded more than 80.

A rise in incidents has forced authorities to increase security around schools and led to calls for more research into the root causes of such acts.

The Guangxi region, where Friday's attack occurred, was the scene in September 2012 of an attack in which a man wielding an axe killed three children and injured 13 others.

State media reported in January that the man, Wu Yechang, was sentenced to death for the attack and appealed but the motion was rejected by a higher court on Wednesday and will now go to the Supreme Court.