China has ordered one of the most popular virtual private networks (VPNs) in the country to cease its operations amid a nationwide clamp down on internet freedoms, Bloomberg reports.
VPNs are used the world over to bypass state imposed internet access restrictions. They work by routing traffic to servers in locations where those restrictions don’t apply. In China, where a system known as the Great Firewall blocks access to news sites such as the New York Times, social media sites like Facebook, and a raft of other content, VPNs are used by private citizens, businesses, universities, and even state-run newspapers to get to off-limits information.
Read more: China’s Great Firewall is Harming Innovation, Scholars Say
But on Monday GreenVPN, one of China’s most popular, told customers it would freeze its service on July 1 after “receiving a notice from regulatory departments.” Some users reported being unable to use the VPN on their smartphones over the weekend, although it is unclear whether this was down to a glitch or the restrictions.
For more on government internet censorship, watch Fortune’s video:
The move is just the latest tightening of internet censorship in the run up to the Chinese Communist Party’s 19th Congress, due to be held around October. Last month, China’s media oversight body ordered three major online companies — including the Twitter-like micro-blogging platform Weibo — to halt some of their multi-media streaming services.
In a January proclamation, China’s Ministry of Industry and Information Technology listed restricting VPNs as one of several priorities for controlling online content in the country.