INTERNET regulators in China have warned online services, including Alibaba Group Holding Ltd., against carrying illegal content such as virtual private networks (VPN) that help users bypass its censorship actions.

On Thursday, the Cyber Administration of China named Alibaba’s Taobao Internet bazaar as among five services that needed to rectify related issues immediately, Bloomberg reported.

Users had told the regulator they found “controlled substances”, including VPNs used to access foreign websites, for sale in Taobao.

According to Bloomberg, the warning came amid Beijing’s clampdown on restricted Internet usage in the lead-up to the prominent Communist Party Congress scheduled for later this year. The congress is expected to see President Xi Jinping consolidate his authority.

In a statement, Taobao, the country’s largest online marketplace, said it was unclear what the regulator meant by illegal substances, as such content would cover items ranging from drugs and pornography, among others.

It did, however, maintain it would continue its efforts to bar illegal products, in line with its policies.

“Taobao forbids the listing or sale of any products that are forbidden by applicable law,” Alibaba was quoted as saying.

“We screen and remove product listings from third-party sellers which violate our marketplace rules.”

China held a drill on Thursday with Internet service providers to practice taking down websites deemed harmful, as the country’s censors tighten control ahead of a sensitive five-yearly political reshuffle set to take place later this year.

Internet data centres (IDC) and cloud companies – which host website servers – were ordered to participate in a three-hour drill to hone their “emergency response” skills, according to at least four participants that included the operator of Microsoft’s cloud service in China.

Earlier this month, China’s Public Security Ministry called for the drill “in order to step up online security for the 19th Party Congress and tackle the problem of smaller websites illegally disseminating harmful information”.

Xi has overseen a tightening of China’s cyberspace controls, including tough new data surveillance and censorship rules.

The drill asked Internet data centres to practice shutting down target web pages speedily and report relevant details to the police, including the affected websites’ contact details, IP address and server location.

China has been tightening its grip on the Internet, including a recent drive to crack down on the usage of VPNs to bypass Internet censorship, enlisting the help of state-owned telecommunication service providers to upgrade the so-called Great Firewall.

In late July, Apple removed VPN apps from its app store, while Amazon’s China partner warned users not to use VPNs.