China has largely blocked Facebook-owned encrypted messaging app WhatsApp ahead of a Communist Party gathering in October, The New York Times has reported.
WhatsApp has experienced some disruptions since mid July, with users unable to send audio and video chats, photos, and other files. Users could still send text communications at the time, and the restrictions were lifted after several weeks, according to the publication.
However, the report said that WhatsApp users in China can no longer send texts now, though the app is partially accessible to some users in some parts of the country.
Data from the Open Observatory of Network Interference suggests the block may have been implemented on September 23.
"Losing contact with my clients, forced back to the age of telephone and email for work now," one user, cited by the NYT, complained on Weibo.
"Even WhatsApp is blocked now? I'm going to be out of business soon," another person wrote on Weibo, according to the NYT.
The move is said to be a blow to Facebook, since the social media giant has been pushing to re-enter the market. Facebook has been banned in China since 2009.
The Chinese government has long controlled online speech through censorship, harsh punishments, and by blocking numerous websites such as Google, Instagram, Twitter, and YouTube in favour of more restrictive localised versions.
In July, images of the late Nobel Peace Prize-winning human rights campaigner Liu Xiaobo were being blocked in direct messages between users on WeChat and Weibo. Throughout his life, Liu called for political reforms, and was imprisoned in 2009 on charges of subversion for calling for democracy in China.
But the blocking of WhatsApp is part of a wider trend of tightening controls and restrictions under President Xi Jinping.
Humans Rights Watch previously said that internet control "has reached new heights" since Xi became president in March 2013, with the government criminalising the "spreading of rumors" about natural disasters and virtual private networks being described as "terrorist software", among other occurrences.
The government has additionally been cracking down on VPN apps so that Chinese citizens cannot circumvent censorship. In July, Apple sent notifications to developers in China explaining their VPN app was removed from the Apple App Store, as the apps included "content that is illegal in China, which is not in compliance with the App Store Review Guidelines".
In November last year, Chinese legislature, the National People's Congress Standing Committee, passed a new cybersecurity law to protect the government's sovereignty on the internet, national security, and citizen rights.
The law, which came into effect on June 1, bans the collection and sale of customers' personal information, with companies also having to store customer data on servers in the country, though the latter has been delayed until the end of 2018. Customers will have the right to have their data erased, although they will have to register with their real names on messaging apps and social networks.
The law also stipulates that parties involved in criminal activities online will be punished, as will individuals and organisations that attempt to "overthrow the socialist system", "fabricate or spread false information to disturb economic order", "incite separatism or damage national unity", and "advocate terrorism or extremism".
Other forbidden activities under the new cybersecurity law include the incitement of ethnic hatred, discrimination, and the spread of violence and "obscene" information.
The State Council will be also able to authorise or take temporary control of network communications in response to incidents threatening public security. This provides a legal basis for large-scale network shutdowns.
Network operators are obligated to cooperate with the government during investigations under the new law. This includes the reporting of "network security incidents" as well as the provision of "technical support" to security agencies.