The death of a teenager at an Internet de-addiction centre in China has again brought into sharp focus the country's controversial camps to cure obsessive online habits among adolescents and young adults.

The parents of Li Ao, 18, were informed their son had died within two days of being admitted to the internet boot camp in eastern Anhui province's Fuyang city earlier this month, the Anhui Daily reported.

The daily quoted the parents as saying that the centre had advertised that it cures Internet addiction through counselling and psychological counselling, and not by using methods that could prove physically harmful to the inmates.

The parents, however, discovered several bruises and scars on their son's body, which aroused their suspicion.

"My son's body was completely covered with scars, from top to toe...When I sent my son to the centre he was still fine, how could he have died within 48 hours?" Li's mother was quoted as saying by the Shanghaiist website.

Senior camp officials have been taken into custody but the reason for the death is yet to be ascertained.

According to the Sixth Tone news website, in 2008, China became the first country to recognise Internet addiction as a clinical disorder.

"Health officials divided the disease into five categories of addiction: online games, social networking, shopping, pornography, and the nebulous 'Internet information'," a report said.

Earlier this year, the government drafted a regulation banning electric shocks and beatings to wean teenagers off the internet.

The number of such boot camps in China is not officially available but reports often describe their style of functioning as "military".

At one centre in Shandong, an inmate killed her mother last year, apparently because of the abuse she faced in the name of treatment.

A report released by the China Internet Network Information Centre in January stated that 170 million under-18s are online in China, while 43.7% of them spend more than an hour on tablets and smartphones each day.

By June last year, about 23% of the 710 million internet users on the mainland were aged under 19, according to Legal Daily. More than 90% of adolescents used the internet, the report added.

"In May, the ministry of culture issued a statement to strengthen the identity registration system in online games to control payments made by children, as according to the Civil Law, those under 10 have no capacity for civil conduct, while for those aged between 10 and 18, it is limited," the report said.