HONG KONG: 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.

China's Ministry of Public Security 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", according to a document circulating online attributed to a cyber police unit in Guangzhou.

An officer who answered the phone in the Guangzhou public security bureau confirmed the drill but declined to elaborate.

President Xi Jinping has overseen a tightening of China's cyberspace controls, including tough new data surveillance and censorship rules. This push is now ramping up ahead of an expected consolidation of power at the Communist Party Congress this autumn.

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's Ministry of Public Security and China's cyberspace administration did not respond to faxed requests for comment.

Several service providers, including 21Vianet Group and VeryCloud, issued notices to users, warning of possible temporary service disruptions on Thursday afternoon as a result of the drill, which were confirmed to Reuters by their customer service representatives.

Nasdaq-listed 21 Vianet Group is China's largest carrier-neutral internet data centre services provider according to its website, and counts many Western multinationals including Microsoft, IBM, Cisco and HP among its clients. It runs Microsoft's Azure-based services in China.

21 Vianet Group did not immediately respond to an emailed request for comment.

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.

Apple last week removed VPN apps from its app store, while Amazon's China partner warned users not to use VPNs.