Japan's mobile messaging platform LINE may be preparing to censor politically sensitive phrases in China, following in the footsteps of Tencent-owned WeChat.

This was spotted by Twitter user @hirakujira who posted a tweet indicating his or her research found LINE had a mechanism which will detect and restrict the use of certain phrases on its China service, Lianwo, The Next Web reported. The Twitter user appears to be Taiwanese, and posted from Hsinchu City late on Tuesday.

While the censorship feature has yet to be switched on, the Twitter user had proved the feature exists by hacking his or her iPhone to get packets from LINE, which generated the following notification in Mandarin which reads "Your message contains sensitive words, please adjust and send again", when translated to English.

The Next Web noted @hirakujira also gained access to Lianwo servers and obtained a list of 150 "bad words" which the company will monitor and posted it on PasteBin. Some of the phrases include Tiananmen Square massacre, a phrase which got Foursquare blocked in China and recently ousted Prime Minister Wen Jiabao and his family wealth, the subject of an expose in The New York Times.

LINE currently has 45 million registered users in Japan, but has passed the 150 million milestone worldwide with fast growth in Southeast Asia, Spain and Latin America. Despite WeChat's dominance in China , LINE launched there in December 2012, and its lack of censorship had been an advantage it had over WeChat.

[UPDATE: May 23, 5.15 p.m.] In a statement to ZDNet , LINE confirmed the censorship feature exists but maintained the feature only applies to the Lianwo server.

"Lianwo has been optimized to serve the local environment in accordance with mainland China's standards, which does not affect the global service of LINE," a company spokesperson said.