The 39-year-old woman entered the school in Banan district when the children were in the playground, the BBC reported.

Although the authorities have not said anything about the motive behind the attack, social media reported that the woman had a grievance against the government.

Mentioned by her surname, Liu, was arrested from the scene.

The police have denied media reports that said two children were killed. They also urged social media users to refrain from passing on "rumours", the BBC report said.

China has faced a string of unrelated knife attacks in schools and kindergartens over the last few years. They have usually been carried out by people seeking revenge against officials or individuals, or those ailing from mental illnesses.