Three children have been killed and six more people injured in a knife attack at a school in China's central Hubei province, state media report.

The attack took place at the Dongfang primary school in Shiyan city on Monday morning.

Police said a man in his forties stabbed eight children and an adult and then killed himself by jumping off a building, Xinhua news agency reported.

Local police said that an official investigation was underway.

Citing an initial police investigation in a post on its official microblog, Chinese state broadcaster CCTV news said that the man was "a parent of a student".

He had carried out the attack after the school "refused to allow his daughter to register for the new term on Monday" because "she did not finish her summer homework", CCTV said.

China has increased security measures in schools in recent years following a series of similar attacks, generally attributed to people with personal grudges or suffering from mental health problems.

In March 2010, a man stabbed to death eight students at a school in China's south-eastern Fujian province.

Police said the attack was caused by his break-up with a girlfriend. He was executed soon afterwards.

Another knife attack in 2010 saw at least three children killed and more than 20 students and staff injured at a Chinese kindergarten in Shandong province.