The Chinese government issued a circular Monday to tighten restrictions on online transactions of drug precursor chemicals, in a bid to fight Internet-enabled drug trafficking.

According to the circular jointly issued by five government departments including the Ministry of Public Security and the Ministry of Industry and Information Technology, individuals are banned from selling precursor chemicals - that is, chemical substances that are used to manufacture narcotics - over Internet.

Only companies having a license to produce and sell these chemicals are allowed to publish sales information online, the circular said.

In addition, when it comes to four chemical substances on the strictest control list - such as ephedrine and lysergic acid - no individuals nor organization is allowed to trade online.

Operators of business websites are required to carry out strict checks of precursor chemical suppliers, submit photocopies of their licenses to Internet service providers, and publish the formal name of suppliers and their license numbers on the website, the circular said.

"As e-commerce in China grows quickly, drug dealers are taking advantage of the Internet for making anonymous transactions. In recent years, the Internet has become a key channel for drug dealers to trade precursor chemicals," Zhang Xinfeng, vice minister of public security, said in an interview with Xinhua.

Zhang cited a drug gang cracked by police in eastern Shandong Province in August, when police arrested 42 suspects. The two ring leaders learnt how to cook dope, buy chemicals and equipment, and sell the drugs all online. They even recruited dealers online to sell their dope.

Precursor chemicals are commonly used in industry, agriculture and daily life, Zhang said.

"But once they fall into the wrong hands, they could be made into dangerous drugs," he added.

Only one factory on the Chinese mainland is licensed to produce Hydroxyl Imine, the main ingredient of Ketamine, and it has not started production, he said.

Even so, "there are more than 200,000 hits for the chemical when it is searched for on the Chinese Internet."

From 2006 to 2009, Chinese police cracked 1,554 cases of illegal trade in precursor chemicals and confiscated 3,814 tonnes of such chemicals.

Internet service providers should also improve the management of online forums and delete unlawful information about these chemicals and report it to the police, the circular says.

Besides issuing the circular, the authorities will also launch a nationwide campaign to check business websites and delete illegal information about precursor chemicals, Zhang said.

"We will try our best to facilitate the legal trade of precursor chemicals online while cracking down on crime."