Top: Children at Beijing Stars and Rain Education Institute for Autism stage a performance during a charity banquet in Beijing. Above: A teacher at Beijing Stars and Rain Education Institute for Autism provides one-on-one coaching to a child. Photos provided to China Daily

Four in every 1,000 children aged 6 to 12 in China have autism, an incidence that experts say is higher than expected.

The figure has been uncovered in the first national epidemiological investigation into the prevalence of autism spectrum disorder.

Symptoms include differences and disabilities in many areas including social communication skills, motor skills, and sometimes intellectual skills as well as unusual responses to sensory input such as unusual sensitivity to light and sound, or sensory cravings.

The investigation figures did not include those children who stay at home or those in special schools, as they had already been diagnosed as ASD patients, said Wang Yi, vice-president of the Children's Hospital at Fudan University in Shanghai, which led the project.

More than half of the children in the project were diagnosed with autism for the first time, Wang said.

"Such data obtained at the national level for the first time shows that ASD is much more serious than we imagined. The figure is close to the incidence rate of epilepsy among children in China," Wang said.

The statistics were announced at the International Meeting for Autism Research in Shanghai on Saturday.

China is not the only country with a high incidence of autism. Last year, the United States' Centers for Disease Control and Prevention said one in every 68 children in the US has autism.

A total of 127,000 children were involved in the Chinese project, started in May 2013.

Geraldine Dawson, a professor of psychiatry and behavioral sciences at Duke University in North Carolina, said babies who later develop autism exhibit behavior suggesting that some symptoms emerged when they were just 6 months old, and that parents should be alerted.