Mobile chat app Line and web services disrupted in China
Several popular messaging applications and file-sharing services appear to have been blocked in mainland China this week.
These include mobile messaging apps Line, which is widely used in Asia, and Kakaotalk.
Yahoo's photo-sharing service Flickr and Microsoft's file storage service OneDrive have also been affected.
The move appears to have taken place ahead of a major pro-democracy protest in Hong Kong on Tuesday.
China already blocks popular social media services Facebook, Twitter and Youtube.
Yahoo told agencies that it was investigating the situation, while Line said on its Weibo account that it was working to fix the problem.
The disruption has affected users of Line in particular. The service has more than 400 million users, mostly in Asia. Thousands of Chinese users have flooded Line's Weibo account with complaints.
A Line spokesman told Bloomberg that its users in China had not been able to access all services since 1 July, which was the anniversary of Hong Kong's handover to the mainland.
Tens of thousands took to the streets of Hong Kong that day in a major pro-democracy protest.
A representative of anti-censorship site GreatFire.org told Reuters news agency this was not a technical malfunction, suggesting the services were blocked because they allowed users to share photos.
Checks by BBC Chinese found that Hong Kong and Taiwan Line users appeared to have been unaffected.
In May, some Line users in China complained that the app had started to censor sensitive terms related to the 4 June anniversary of the Tiananmen Square massacre, according to BBC Chinese.
At that time, Line's spokesman said the China version of the app was being "optimised".